Just as an Xmas present to y'all I am going to type in a bit about 
Ginsberg's yage expedition in 1960.  I will excerpt and paraphrase hunks 
of "Dharma Lion" by Michael Schumacher, which, while quite long, is a fun 
read even if you're not a fan of Ginsberg (I'm not), as long as you are
interested in beatniks, the '60's and such.  

Ginsberg first used LSD in 1959.  He received an invitation from Gregory
Bateson to experiment with it at Stanford's Mental Research Institute.  
He wrote to his dad, "It was astonishing.  I lay back, listening to music,
and went into a sort of trance state (somewhat similar to the high state
of Laughing Gas) and in a fantasy much like a Coleridge world of Kubla
Khan, saw a vision of that part of my consciousness which deemed to be
permanent and transcendent and identical with the origin of the universe -
a sort of identity common with everything - but a clear and coherent sight
of it."

He later (June 1959) wrote a poem, "Lysergic Acid," part of which goes like:

The image or energy which reproduces itself at the depths of 
	space from the very Beginning
in what might be an O or an Aum
and trailing variations made of the same Word circles round
	itself in the same pattern as its original Appearance
creating a larger lineage of itself throughout depths of Time
outward circling thru bands of faroff Nebulae & vast Astrologies
contained, to be true to itself, in a Mandala painted on an 
	Elephant's hide,
or in a photograph of a painting on the side of an imaginary
	Elephant which smiles, tho how the Elephant looks is an
	irrelevant joke - 
it might be a Sign held by a Flaming Demon, or Ogre of 
	Transcience,
or in a photograph of my own belly in the void...

In January 1960 he went to Santiago, Chile to a writers' conference.   After
the conference he wandered around northern Argentina, then went
back to Santiago, and got some grant money and some unexpected money
from poetry sales that allowed him to pursue his plan to go to La Paz,
Bolivia.  "According to his plan, he would stay in La Paz for two or
three weeks, sightseeing and waiting for his mail to arrive, and from there
he would proceed to Peru, where he would hook up with people who could 
direct him to sources of yage."

He went to Lima, where William Burroughs had been exactly 7 years ago.
Burroughs had given Allen instructions on how and where to get yage.
He contacted a doctor who helped him get some ayahuasca, and he tried
it in his Lima hotel room on May 23.  "He had received a jar of an
already-prepared solution that was nowhere near as potent as the 
mixture made by the Amazonians Burroughs had written about, but
the experience was memorable nevertheless... `I drifted away in bed
in darkened hotel room and came to the gate of heaven and yelled in 
my mind, `I am back home in the house of the splendid ancient Lord, and
I am the son of the Lord, in fact I am the lord himself come back home
and I want the gates open.'  Got a minute of feeling near Union, but
the dose was too small & I was too amazed to get completely lost.'"

He then went to Pucallpa, a town on the edge of the Ucayali River that
Burroughs had recommended as a source of yage.  It was a slow, rough
trip.  Once he got there, he looked up a local authority on yage, who
put him in touch with a curandero willing to give him some ayahuasca.  
"Known as Maestro, the curandero had studied under a witch doctor and
grew his own Banisteriopsis caape plants to use in his yage brew.  The
ritual was held in the evening, and on a typical night there would be a 
group of five to thrity people taking the drug.  On his first night,
Allen was given a dose of older and slightly fermented yage that, though
still more powerful than the earlier dose he had taken in Lima, did not
produce the violent nausea and powerful visions that Burroughs had written
about from his experiences.  About 45 minutes after drinking the liquid, 
Allen had a sense of being in the presence of `the Great Being,' which
was manifest in the form of an eye staring from a great black hole 
surrounded by hallucinatory apparitions of snakes, fish, butterflies,
birds, and other creatures symbolizing, as far as he could tell, the
entirety of creation.  The feeling was pleasant.... The effects of the
drug lasted about three hours.  Allen had no sooner returned to his normal
state when he began to look forward to his next experience."

Let's just recall that Burrough's experiences were indeed far more
intense.  When Burroughs had taken the drug, he was violently nauseous,
dizzy, numb in the limbs, and chilled.  He wrote, "Larval beings 
passed before my eyes in a blue haze, each one giving an obscene, mocking 
squawk," and had imagined himself to be alternately a man and a women in a 
delirium that lasted for nearly four hours.  So Ginsberg clearly knew
there could be more to the yage experience than a wimpy "Great Being" 
vision.  :-)

"However, it was different the next night, when he took a fresh and 
therefore much stronger dose.  Maestro served the yage ceremoniously,
blowing smoke over the enamel cup and humming a melancholy song before
he handed it to Allen.  As he felt himself getting high, Allen lay
down on the ground waited, expecting the same kind of pleasant visions
as he had experienced the night before.  Instead, as he reported to 
Burroughs, `the whole fucking Cosmos broke loose around me':  `I felt
faced by Death, my skull in my beard on pallet on porch rolling back
and forth and settling finally as if in reproduction of the last
physical move I make before settling into real death - got nauseous,
rushed out and began vomiting, all covered with snakes, like the Snake
Seraph, colored serpents in aureole all around my body.  I felt like
a snake vomiting out the universe - or a Jivaro in head-dress with fangs
vomiting up in realization of the Murder of the Universe - my death to
come - everyone's death to come - all unready - I unready...'"

"Even as he was experimenting with drugs, he knew they were not the
answer.  He wanted something pure, a higher consciousness attained without
the use of artificial means.  Still, as long as he had reached the level
of consciousness he had under the influence of yage, he would not abandon
the drug.  Since his childhood days and his Shrouded Stranger fantasies,
he had been terrified of facing death, God, or whatever supreme 
consciousness was out there.  Although, as he told Burrough, he was not
certain of the price he would pay for staring into the void, he would
continue his quest until he had answers for some of his questions."

"Night after night, he returned to Maestro for more yage, and each day 
following, he would write about the experience in his journals...."

Later, wanting to try ayahuasca from other parts of Peru, he went to
Iquitos, a port on the western end of the Amazon.  "As he suspected,
the yage brewed in the Amazonian region of Peru differed from that which
he had taken in Pucallpa.  The mescla used as a catalyst in the mixture
was different.  Allen was eager to try it, as well as bring home a sample
for later consumption.  After a week in Iquitos, he located a man living
at the outskirts of the city who was willing to give him a dose.  On June
24, he took three swallows of ayahuasca from a small gourd cup, and, while
the brujo sat nearby, tapping his foot and whistling a tune, Allen was
delivered to a multidimensional universe watched over by a serpent so
huge that ithe middle of its body and tail disappeared into the void.  
The whistling sound became part of the vision - the sound the serpent 
made to signal `its Eternal presence at all times and place.'  The serpent,
for all its gigantic and powerful presence, was not entirely frightening.
It promised a resolution to death, the entrance into its spirit and
the understanding of this consciousness.  The vision seemed to imply
that death, although unavoidable, was not as terrifying as Allen had
imagined it.  Death, he reasoned, was the breakdown of a familiar 
dimension."

"The next day, he was on a plane heading back to Lima...."