"I was on all fours convulsed with spasms of nausea," William Burroughs wrote to Allen Ginsberg, describing a yagé session. "I could hear retching and groaning as if I was someone else. I was lying by a rock. Hours must have passed."

The year was 1953. Burroughs went down to Colombia searching for yagé. At that time, the drug was virtually unknown in the West. The 39-year-old Burroughs had heard rumors of it as "the ultimate kick" and as a potential cure for heroin addiction.

Burroughs was a desperate man. An aging trust-fund brat, heroin-addicted, homosexual, Burroughs had killed his wife several years earlier, drunkenly shooting her through the head at their home in Mexico City. It was a party trick gone wrong - but Burroughs knew it was more than that. He felt he was possessed by evil spirits, that he was damned. He went to the Amazon in search of yagé, hoping his visions could redeem or exorcise him somehow, that the hallucinogen would free him from his dependence on junk. In Bogota, he met the legendary Harvard botanist and Amazonian explorer Richard Schultes. The two Harvard alumni hit it off. Burroughs attached himself to one of Schultes' botanical expeditions.

He took the plant brew with several brujos in the Amazon jungle. After some misfires, Burroughs was given his visions - not visions of light and life and self-regeneration, but visions of dark mergings and dissolutions and horror. "Larval beings passed before my eyes in a blue haze, each one giving an obscene, mocking squawk (I later identified this squawking as the croaking of frogs)," he wrote to Ginsberg after an early session in which he vomited six times.

"Yagé is space time travel," he wrote from Peru, after many misadventures and traumatic trips. "The room seems to shake and vibrate with motion. The blood and substance of many races, Negro, Polynesian, Mountain Mongol, Desert Nomad, Polyglot Near East, Indian-new races as yet unconceived and unborn, combinations not yet realized passes through your body."

The drink gave Burroughs entry to the "Composite City where all human potentials are spread out in a vast silent market… The city is visited by epidemics of violence and the untended dead are eaten by vultures in the street." Although he only took yagé a few times, it is possible to argue that the yagé visions had a much deeper effect on his fiction than his use of heroin. His Amazonian visions of a sleazed-out "composite city" became the atmosphere of Naked Lunch, written a few years later, with its dissolutions of identity; urban wastes of festering plagues, sex manias, and sadistic control freaks. Even the montage-like breaks that characterize his mature style call to mind the overlapping hallucinations of the Amazonian brew.

The infinite murmuring vista of urban sleaze and cheap kicks and blank death that Burroughs discovered on yagé was probably not the vision he wanted. But it was the vision he needed.

I think that, even before I tried ayahuasca, I had some intuition about what it was. In the Amazon, yagé is "the medicine," "the purge," "the vine of souls," "the rope of death." It is the substance that reveals the Amazonian Indian cosmology, source of indigenous wisdom. The shamans of the Amazon say that all of their knowledge - of the plants and the spirit world - comes from ayahuasca.

We live in a culture where everything tastes good but nothing satisfies. At our core, we remain insatiable, constantly on the prowl for new commodities and pleasant sensations to fill the void. "Life tastes good," proclaims an ad for Coca Cola. Yagé, on the other hand, tastes extremely bad. It is a bitter concoction, made of the bark of a vine and the leaves of a shrub. The flavor is like the distilled essence of forest rot. Yagé drinkers vomit and shit, shiver and sweat, and at the same time receive outrageously beautiful visions. The potion is an antidote - following Benjamin, I am tempted to say a dialectical cure - for our current condition. As a hipster shaman told me at Burning Man, "White man medicine make you feel good first, bad later. Indian medicine make you feel bad first, good later." Many people report feeling both physically and psychically recharged after yage - I certainly do.

I first drank the brew with strangers, wearing Adult Depends diapers and a blindfold, sitting in a small, drab apartment overlooking the East River. New Age-sounding tribal music played on a tape deck. Initially, I saw, as Burroughs had, images of grey squalor - bodies lying in the gutter of an anarchic slum, animals at a trough. I had a momentary vision of bright emerald-green vines waving in front of a blue waterfall. Afterwards, for a long time, there was nothing else. I listened to the gasping and retching of the woman sitting across from me. She was horribly sick for hours. The guides tried to help her, but to no avail.

The Indians revere ayahuasca for its healing powers. The purging of parasites and toxins is part of the healing process. I felt like an alien intelligence was coursing through me, examining my organs and nerves and cellular processes, making subtle adjustments. It was like I was a computer and ayahuasca was a program performing scans and repairs. When it had done its work, I threw up - the vomiting was like the beep at the end of a program.

My thoughts drifted off. I watched a scene taking place within my mind. Particles, like little flares of light, gathered into clouds that floated upwards - when they arose, the focus of my awareness would suddenly shift to a different subject. I realized I was watching a model of thinking, of the neurochemical process of my subconscious creating thoughts. These clouds were synaptic concentrations, neural nets; one after another, they floated to the surface of my consciousness. When the information reached a sufficient density, "I" would be presented with a new perception.

This vision was a small revelation. I realized that most thoughts are impersonal happenings, like self-assembling machines. Unless we train ourselves, the thoughts passing through our mind have little involvement with our will. It is strange to realize that even our own thoughts pass by like scenery out the window of a bus - a bus we took by accident, while trying to get somewhere else. Most of the time, thinking is an autonomous process, something that happens outside of our control. This perception of the machine-like quality of the self is something that many people discover, then try to overcome, through meditation.

Ayahuasca is sophisticated jungle chemistry. The Amazonian potion usually consists of two ingredients, the bark of the ayahuasca vine (banisteriopsis caapi, which grows in thick double-helix-shaped coils around rainforest trees) and the leaves of psychotria viridis or some other plant. The vine contains a class of psycho-active and sedating drugs called betacarbolines, which includes harmine and harmaline. The leaves have NN-DMT in them, a highly potent hallucinogen that is also produced within the human body, in the base of the spine and the brain. Although powerful when extracted and smoked, DMT is not orally active. Mono-amine oxidase (MAO) enzymes in the gut break it down before it reaches the brain. You can eat pounds of the stuff without feeling an effect. However, the betacarbolines in the vine are natural MAO inhibitors, which means they allow the DMT to work. The ayahuasca brew, according to Santo Daime, a Brazilian religion which takes yagé as its sacrament, is a combination of the "force" of the vine and the "light" of the leaves.

DMT, smoked alone, creates a rapid-fire visionary experience, an overwhelming immersion in an extremely alien world that lasts less than ten minutes. The betacarbolines, taken alone, create subtle, monochromatic hallucinations that are soft, warm, and humanized. A friend of mine described seeing compassionate maternal faces floating over him after a strong dose. Mixed together in the ayahuasca brew, the betacarbolines seem to have a pacifying and humanizing effect on the DMT visions, acting like an interface, and they stretch the experience out from a few minutes to a few hours. It is unknown how Indians, living among hundreds of thousands of plants in the forest, learned to combine these botanical ingredients, which are usually boiled together for several hours. The Indians say that the ayahuasca vine taught them how to do it.

The more I learned about it, the more I was fascinated by ayahuasca. Even the taste seemed to change in my memory from something simply horrible to something horrible that I yearned to taste again. But the opportunities to find it in New York were few and far between. Finally, a year after that first session, I found the right ingredients and cooked up a brew for myself and two friends. I used plants that differed from the traditional Amazonian sources. In the last decades, many other plants have been found with identical chemical compounds, sometimes in much more concentrated amounts. Botanists have discovered DMT, especially, in a wide range of flora, including some common grasses. My brew was made from the reddish DMT-containing bark of mimosa hostilis and a black powdered extract of Syrian Rue, a Near Eastern plant that produces a mixture of betacarbolines, like the ayahuasca vine. Syrian Rue has an ancient history of ritual use in the Near East. Some researchers have suggested that the reddish geometrical patterned hallucinations caused by ingesting Syrian Rue may be the historical origin of the patterns on Arabian carpets - as well as the source of the Arabian myth of flying carpets.

I followed the recipes of Jonathan Ott, whose book Ayahuasca Analogues describes how to make ayahuasca-like compounds using plants from every hemisphere. "I hope the simple home technology described in this book will drive the last nail into the coffin of the evil and hypocritical … crusade to eliminate this class of drugs from the face of the earth," he writes in his introduction. "May the Entheogenic Reformation prevail over the Pharmacratic Inquisition…"

Cutting up the plant matter, grinding it into powder, and boiling it down took an entire afternoon. The woodsy aroma of the broth permeated the apartment. Within an hour of drinking the vile stuff, both of my friends threw up violently and repeatedly. They thought I had poisoned them.

Soon enough, shuddering, I followed them to the bathroom and threw up. Afterwards I felt, spreading through me, a magnificent sensation. I felt cleansed and strong as the yagé opened my visionary capacity. I lay on the couch as my psychic periscope rose into the imaginal realms.

Images coiled around the sounds from the stereo. We played Javanese gamelan, Ravi Shankar, Ornette Coleman, Bach. The dead skin around perception was peeled away to reveal new levels of sensory subtlety. Music was like a physical event permeating the cells, opening new pathways through the psyche with every change in phrase.

Images crowded into my mind - faint, fragmentary, flickering. I entered viny jungles, shot through the abandoned reaches of outer space. Pictures formed and dispersed at high speed. Geometric mandala patterns appeared and faded. I watched twisting forms that were tubular, tentacular. Suddenly I seemed to be on a spaceship. The creatures piloting the ship shook their long spindly limbs at me in greeting. They were plant-like, shaking their stalks and blossoms to show me their other-world comedy.

I removed my blindfold and looked around. The room was shimmering, pulsing with waves of light. I felt I was inside the liquid material, the flowing invisible currents, of my dreams. The hallucinations seemed to happen in a psychic space between willing and letting go. If I tried to force the visions, they evaporated. If I didn't pursue them, they also disappeared. There was, I realized, a skill to perceiving them, an internal effort that required utilizing a form of seeing that was disconnected from normal vision.

I held a metaphysical dialogue, unsure if I was conversing with some higher aspect of myself or the plant-spirit, or both. I tried to interrogate that elusive "other" about the nature of life and death, the holographic universe, the spirit realms. The response was something like a suppressed giggle.

The thought came to me that human consciousness is like a flower that blossoms from the earth. The stem and the roots are invisible cords, etheric filaments that lead back to a greater, extra-dimensional being. Our separation from that larger being was only a temporary illusion. The universe was, we would know if we could perceive its workings, purposeful and good.

Then I was looking up from my grave as dirt was thrown on my coffin. Yet this horror movie vantage point didn't bother me. It made me feel calm.
We were listening to Ravi Shankar play the sitar, a woman singing with him. The music was a seductive whispering tale. Each slow melodic riff announced itself then insinuated its message like a teasing sexual possibility. Images and ideas licked out like tongues of shape-shifting flame. There were rainbow-tinged tunnels drawing me forward, visual echoes of carnival worlds and orthogonal entryways to schizoid paradises of possibility. At the end of the night I saw, very clearly, a multi-armed Shiva dancing before me. He broke apart into flimmering octopus arms, writhing plant forms. Soon after that, the visions ended.

That night, my two friends had little to report besides extreme nausea, and an expansion of their senses. Later, after other successful and failed trips, I understood that is part of the deal with ayahuasca. Compared to other psychedelics, yagé's effects are extremely unpredictable - depending perhaps on the weather, the dream you had the night before, your horoscope. It can unveil the shamanic rainbow, access the universal serpent-power, or it can leave you vomiting and visionless. In a perverse way, for me at least, that is part of what makes the brew so appealing. Unlike LSD or mushrooms or Ecstasy, yagé cannot be commodified or consumed recreationally - its gnosis must be earned.