Jonathon Miller-Weisberger met Don Caesario seven years ago at a conference held in the Secoyas' ancestral homeland, La Garta Cocha, near the headwaters of the Amazon. "I had such a fun time with this old guy," said Jonathon, who could sound like a West Coast dude at one moment, deadly serious mystic explorer the next. "I spent three weeks with him at his home, laughing all the time, sleeping under the same mosquito net. His house had fallen down, and he was living with his son. He asked me to help him build a new house."

Jonathon had learned about the Secoya when he was a kid growing up in Quito, where his mother ran a vegetarian restaurant (she is now studying anthropology in Berkeley). He found a postcard of a Secoya at a bookstore. "I saw this totally rad-looking Indian wearing this yellow crown, with flowers around his arm, strings of beads, and I thought, Wow, I would love to meet that guy," he recalls. Years later, he heard a story about a Secoya who got lost in the forest one night and slept at the top of a tree: "During the night, an evil spirit started to cut the tree down. The Secoya started to sing. He sang to the flowers that blossomed on the tree. The flowers turned into heavenly beings that stopped the evil spirit from hurting him."

Now thirty, he wore blue jeans, beat-up Keds, and a T-shirt embroidered with the "Om" insignia. He practiced tai chi and discoursed earnestly on Eastern wisdom and indigenous mysticism. He was about the same age as Daniel Lieberman, my guide in Gabon. Like Lieberman, he was Jewish, dark-haired, thin, an idealistic outsider with a Buddhist orientation. Encountering Lieberman and then Weisberger, it seemed as if I had stumbled across some contemporary archetype - the young ethnobotanist as wandering Jewish sage.

Jonathon called Don Caesario "a saint of yagé" who had "achieved spiritual immortality." He told us that Don Caesario is the tribe's last great shaman, a once-prestigious leader who lost his authority. With the exception of a few elders, the tribe has stopped following shamanism over the past thirty years. Even Caesario's son, Caesar, was an evangelist, converted by the missionaries. Although Caesar was the tribe's community president, like most of the younger Secoya he wore Western clothing. He never drank yagé.

In an evening ceremony, we met the last upholders of the tradition, the tribal elders, a coterie of dignified gentlemen in colored tunics and yellow crowns who averaged about four foot ten in height. Don Esteban, nicknamed Magico, is a Cofan Indian who married into the Secoya. Esteban wore a traditional feathered headdress, and an iridescent parrot feather through his nose. Don Augustine, nicknamed Tintin, was the apprentice shaman. Tintin rarely said a word - he kept approaching me and then dissolving in mischievous laughter. Don Emilio, we were told, was the master of the forest, with an encyclopedic knowledge of plants and plant remedies. Meeting the elders, I knew I had found what I was looking for, what I had wanted as I pounded the familiar pavement of New York City: As much as they were perfectly present, the elders also had the eccentric aura of mystics, of sages who travelled far into distant visionary realities and returned to giggle about it.

Don Esteban stood up and told us the story of his life. He had been a shaman in his youth, but when the missionaries arrived he assumed that Christianity had greater power. He abandoned his traditional spiritual culture and became a Christian, working with the missionaries. They told him not to take ayahuasca, so he didn't. But as time went on, he realized that as a Christian, he was no longer able to heal anybody. A nephew of his died, and he knew that with ayahuasca he would have been able to heal him. He decided that Christianity didn't have all the answers and he returned, after a thirty year absence, to ayahuasca. He also said he had tried LSD, given to him by a tourist, and that he could use it to heal as well. "LSD is strong medicine," he said. He promised to help us reach the "deep spiritual realms."

I was ready.

But on the day scheduled for our first yagé ceremony, Don Caesario announced he didn't feel well. Worse yet, he had bad dreams all through the night. The Secoya take dreams seriously. The ceremony was instantly postponed.

Shamanism is a delicate enterprise. Thick coils of the ayahuasca vines grew near the ceremonial lodge. Early that morning, a few of us, myself included, walked up to the vines and looked them over. We even touched them. At breakfast, we learned that our examination instantly gave Don Caesario, who wasn't watching, a splitting headache. Menstruating women also bothered the shaman - Caesario is married, but to keep his spirit pure, he has been celibate for decades - and about half the women in our group were having their "moon." These women were forbidden from going anywhere near the yagé or participating in the ceremonies.

Some of us consoled ourselves with a long hike led by Don Emilio, the forest maestro. In the humid, vine-canopied jungle, my fellow tourists and I, in rubber boots and hiking gear, blundered along like enormous marshmallows next to our quiet, barefoot guide. Don Emilio showed us the Dragon Blood Tree, cutting the bark with his machete to let blood-red sap run out. He carved a thick vine into a wooden eyedropper that slowly dripped sap into our eyes - the jungle version of Visine. He pointed out healing plants clinging to the trees.

That night, I could not sleep. The hike was my first venture into the depths of the rainforest, and the jungle was its own trip. Images of endless plant forms and swaying vines flashed on my closed eyelids like photo prints. Meanwhile, six miles from my hammock, Occidental was drilling an exploratory oil well.

The tiny remnant of the Secoya tribe was struggling to survive. Thieves were only one threat among many: The Indians feared Colombian guerrillas and the herbicides that the US government planned to spray over the coca fields along the border. The Secoya had heard that the poison could kill most of the fish in their river. The biggest fear of all, however, was the encroaching oil company.

In a scene straight out of Apocalypse Now, a large square of land had been cleared in the midst of deep jungle, with helicopters whirling over a two-hundred-foot drilling platform as they dropped supplies into the camp. The drilling, which had been going on since late last year, was currently 8,700 feet deep, and the company had yet to strike oil. If they do indeed find oil, Occidental will build a road straight to the site. The destruction of the surrounding forest and the Secoya culture will soon follow.

Pressured by Occidental and the Ecuadorean government, the Secoya agreed to give access to their land for $700,000, a paltry sum considering the hundreds of millions a successful oil prospect could yield. Even so, the bribes handed out by the oil companies are often enough to destabilize Indian groups who have no practice in economic planning. It is obvious that indigenous groups who up until fifty years ago were strangers to the modern world - who still have a completely different, communal conception of land and property than we do, and no tradition of using money - should not be negotiating with legal teams from the oil companies. But that's been the practice for some time.

In the early 1990s, Jonathon worked on boundary demarcation with the Huarani, a tribe of twelve hundred hunter-gatherers given title to two million acres of Amazonian rainforest. "Nobody ever treated me the way the Huarani treated me," he said. "They were the most proper people I ever met." For Jonathon, the Huarani seemed to exist in a zone of spiritual perfection: "They were totally detached from everything. Even from their own lives." He befriended Wepe, a 100-year-old Huarani who had killed 100 men. Wepe told him, "The tip of my spirit cuts through everything." The Huarani were the only Indians in the region who didn't use hallucinogens - they didn't need them.

At the time, the land title seemed like a major victory for the Huarani, but when the government of Ecuador grants land to indigenous groups, it forces them to forfeit subsoil rights. The once-pristine Huarani territory was now crisscrossed by roads created by the oil companies - followed by the timber companies.

Over twenty years, the wells will produce enough oil to sate U.S. demand for, at the most, two weeks.

"I wept for four days straight about the Huarani," Jonathon said. "I wept until I couldn't weep anymore."

The jungle surrounding the Secoya is facing the same process of shortsighted pillaging. The systematic destruction of the Amazon rain forests - formed over millions of years of evolution, the living lungs of the planet - means ever-accelerating climate change. I have read that some Indian tribes in North America would consider the consequences of their actions seven generations into the future. Our "advanced" society, on the other hand, seems unable to envision the consequences of its actions even a few years ahead.

Two days later, when tensions had subsided, Don Caesario announced we would drink yagé that night. At breakfast I told Pablo Amaringo my dream of the night before. I dreamt that I was drafted to fight in a war. Parts of the dream took place in bootcamp, but it was all quite friendly. Amaringo smiled. "Your dream means that you are being conscripted into the army of the spirits," he told me.

At sunset, we gathered in the lodge, a long thatched building with posts set up for stringing rows of hammocks. The shaman lay in the center of the room, attended by his assistant, Tintin. The Secoya, in their crowns and beads and twined flowers, lay in rows on one side of him, the visitors on the other. There were thirty of us altogether, swaying in our hammocks. Several young Secoya were drinking yagé for the first time, including Caesario's teenage grandson. For one night anyway, they traded in their basketball shorts and sneakers for old-school Secoya tunics and crowns.

I felt bad for Annie and the other women having their "moon." They had come all this way only to be denied the chance to try yagé. Jean-Michel, the Frenchman, backed out, perhaps fearing the psychedelic might undermine his rigid Gallic prejudices.

One by one, we were called up to Don Caesario, who gave us a coconut cup full of yagé, first blowing soft prayers into it. I chugged the bitter brew, suppressing shudders. Eager to push myself as far as possible, I forced myself to go back to the shaman for two more cupfuls of jungle murk later in the night, overcoming spasms of revulsion each time.

I lay back in my hammock as the activity behind my eyelids slowly intensified. Coldness enveloped me. I felt like a caterpillar in a cocoon, immobilized, receptive, fighting the turbulence in my stomach. Time seemed to slow down and distend.

Eyes closed, I saw a grid stretching in all directions. Geometrical forms of strobing spheres and pyramids arose on all of the points of the grid. These forms gave way to shapeshifting geometrical patterns, then more explicit imagery. I saw the vague form of a Mayan-like deity with an animal snout and Indian headdress. I tried to follow him, but he vanished into the ether. I looked into a swirling snake pit at the center of my visual field, where serpents slithered and coiled around each other. The snake pit turned into a field where plants were growing at an incredible velocity, blossoming and then decaying, again and again, and again. An endless profusion of botanical forms rose up, swooned, died, and rotted away. There seemed to be a message to this - that a plant, like every living being, was actually made of energy, the form we see just a temporary snapshot, an illusory interruption of the constant flow, the movement of the spirit.

Every now and then, the images were interrupted by the spasmodic gasps of somebody vomiting in the bushes. As I noticed before, when I took yagé in New York, there was a crepuscular undertone of humor around the visions. I didn't throw up. Later I watched a line of black spacemen slowly filing into a black spaceship. It was a somber, melancholy vision. Finally I understood the meaning of this spaceship. My bowels sputtering, I suddenly needed to find the outhouse. I stumbled out into the jungle. The stars were merry and bright overhead, the banana palms and hovering trees seemed to be welcoming me into the spiritual universe as I sent off my spacemen.

The Secoya sang incredible melodies through the night. Songs of healing magic, chants in a language taught to them by the spirits. Sometimes the songs humorously copied gurgles of nausea or the roar of a wild boar. Don Esteban stood up and let loose with long, unwinding whoops that had the manic ferocity of archaic war cries. A shiver was passing through reality - when I opened my eyes I could see it, like ripples on water - and the songs matched the fast, stuttering rhythm of that shiver.

At moments it felt exactly as if the ceremonial lodge had become a boat or a spaceship, gliding across night-dark water, with Don Caesario calm at the helm. The music was like the rudder leading us forward. I felt tingling vibrations in my teeth, and throughout my body I could sense currents like a magnetic pull following the directions where the songs were carrying us.

The hallucinations started to deepen into a realm that I could not recognize, that I lack language to describe. I found myself wandering across a shimmering space with beings that never stopped changing - porcupine-quilled, tusked, multi-tongued, amoebic, but even those words are only approximations of entities that could be compared to the darker imaginings of HP Lovecraft. The shaman and the elders seemed to be inhabiting this space with me. They sang, their words unintelligible, to these creatures, interacting with them, in mystical communion. It seemed that this was the goal of the ayahuasca ceremony, the arrival point. These were "the heavenly people."

Don Caesario drank another cup of the bitter brew, prepared for him by his assistant Tintin. Then he sang alone. His song seemed to be the wildest and most private ode, a psalm of solitude, unveiling the secret knowledge of his soul. He barely whispered. He breathed into the stars. Then the melody returned, his voice rose up. To my augmented ears, he seemed to be weaving a discourse on reality, on the victory of form over emptiness. As he sang, he seduced a spirit-creature that started to grow, spinning cotton candy filaments around itself. Then Tintin started to sing as well. But he seemed to challenge the shaman's metaphysical viewpoint, arguing that emptiness ultimately triumphs over form. Don Caesario sadly concurred, and the cotton candy creation was released to fall back into the void. Startled by the concreteness of these hallucinations, I did a quick reality check, opening my eyes to the night. The shaman lay back, illuminated by the fire, the other tourists breathed or slept near me in their hammocks.

I had no more doubts that the Secoya engaged in extradimensional exploration, using ayahuasca as their psychic telescope and transport. This was what Jonathon called the "spiritual science of the Amazon." For the Indians there was, I realized, no difference between the natural and the supernatural worlds. Their songs were the chants of spirits calling out to other spirits, weaving through the astral realms.

Later I learned that the Secoya elders say that, through yagé, they can sometimes sing new plants into being. At the end of a long night of pure trance, Don Caesario may look down at his fist to find he is holding a seed or sapling in his palm. He buries that gift from the heavenly people in his garden. In a few months it grows into a medicinal herb, a new remedy to add to their extensive herbarium.

In the morning, we compared notes on our journeys. Some of the travelers were disappointed. Some felt healed or rejuvenated. Tammy, no longer sick, just giggled at the "weird stuff" she had seen during the night - abstract forms, geometrical swirls, trembling entities. "It was totally fun, but I don't know that it meant anything," she said.

Mark and Andrew suffered interminable (you have to take yagé to fully appreciate the meaning of "interminable") nausea and vomiting, and received no visions. Due to some last-second failure of will or nerve, they hadn't pushed themselves to drink more. "It's not my drug," shrugged Mark. He chalked it up to the elusive ways of the "Great Spirit" and seemed relieved to be done with it, ready to go home. Andrew, however, struggled to laugh off his frustration over failing, yet again, to have visions. Like a secretive magician willing to reveal only one trick, the plant refused to show him anything new. Each time he drank, it attacked his guts with more violence.

Octavia said she rocketed through visionary realities. She was led around a museum of archaic artifacts to a small cube of glowing white light. "Pick it up," the spirits urged her. "What is it?" she asked. "It is all the energy in the universe." She decided to leave it alone.

Barbara Nelson and Kerry Locklear, a psychologist and social worker, shared a vision of a small owl watching them. Three others, including a Quechua Indian, saw dolphins spiraling in a blue ocean. (Such "transpersonal" sightings are common on yagé; when the drug was discovered by Westerners in the 1920s, scientists gave it the name telepathine.)

When I tried to tell Don Esteban about my night, he laughed. "Your soul was flying outside your body," he said. "When your soul is flying like that, you can go anywhere you want to go. You can see anything you want to see."

Jonathon burst into the ceremonial lodge with tears in his eyes. Even without partaking of the yagé, he had been up all night - tormented by images of encroaching oil companies, murderous guerrillas, the doomed tribe.

"Where else are you ever going to find old dudes like this who stay up all night to sing for you and heal you?" he asked. "Anyway, nothing ever really goes extinct. We might think it does, but there are a million billion universes out there. Everything that disappears from our world gets reborn somewhere else."