In 1960, Allen Ginsberg wrote a letter to Timothy Leary, then a professor at Harvard. Leary had invited the poet to Cambridge to participate in his studies of the newly synthesized chemical psilocybin. Ginsberg responded with enthusiasm, then listed his qualifications: LSD in 1959, as a subject in a research study at Stanford University; ayahuasca on a trip to South America the following year; nitrous oxide; ether; mescaline; marijuana; datura; opiates. Part II of “Howl,” he added, was “Peyote writing.” His motivation in all this, he explained, was to recover a lost feeling, a “series of mystical experiences—connected with reading Blake” that he had gone through when he was younger.

Leary’s life has been covered extensively, not least in his own memoirs. Trained as a psychologist, he was forty years old and a professor at Harvard when he went to Mexico, in 1960, and tried psychedelic mushrooms for the first time. He returned to Harvard, placed an order with Sandoz, which then manufactured LSD and psilocybin (the synthetic version of the chemical in the mushrooms), and began the Harvard Psilocybin Project with his colleague Richard Alpert (now known as Ram Dass). The invitation to Ginsberg was one of several overtures by Leary to recruit poets and artists for his experiments. After Ginsberg’s visit to Cambridge, he offered to introduce Leary to interested friends, a group that included the publisher of Grove Books, Barney Rosset, the poets LeRoi Jones (later known Amiri Baraka), Muriel Rukeyser, and Robert Lowell, the painters Willem de Kooning and Franz Kline, and the jazz musicians Dizzy Gillespie and Thelonious Monk.

The exchanges between Leary and Ginsberg are collected in a new book, “The Timothy Leary Project: Inside the Great Counterculture Experiment,” compiled by the archivist Jennifer Ulrich, who was put in charge of Leary’s papers when the New York Public Library acquired them, in 2011. Ulrich collects several trip reports here, from Ginsberg and his partner, the poet Peter Orlovsky; from Jack Kerouac; from graduate students and academics; and from Leary himself. They are proto-versions of Internet forums like Bluelight and Erowid, accounts of wonder, awe, and love. “I was experiencing, if not the future, the evolution of our species,” a graduate student named George Litwin wrote of his encounter with otherworldly beings while high on psilocybin. “They were extraordinary people, beautiful, gentle, graceful and full of light.”

“I came home and had the first serious long talk with my mother, for 3 days and 3 nights,” Jack Kerouac reported to Leary. “I learned I loved her more than I thought.”

“Are we Gods ball in his back pocket or are we God with this sun in our heart brain that beams high when on psilocybin,” Orlovsky wrote. “Something beautiful happens & I want more of it.”

As is now well known, Leary soon abandoned clinical protocols, distributing LSD and psilocybin to students and his friends. Leary and Alpert’s nine-page 1962 summary of their initial research, “Americans and Mushrooms in a Naturalistic Environment: A Preliminary Report,” may have been interesting to read, but in response to another proposed study Leary’s supervisors argued that the cause of long-term observational data was not well served by terms like “groovy” and “love engineer.” (Ulrich includes a letter to Leary from a Harvard faculty member instructing him to stop telling Sandoz that his experiments were for the academy.) Harvard fired Leary, in 1963, when his informal dispensary attracted too much controversy. With assistance from the heirs to the Mellon fortune, Leary moved what was still nominally a research institution to Millbrook, in upstate New York. Ulrich includes documents about workshops and courses at Millbrook, as well as an “Experience Planning and Recording Chart” with categories organized into “bardos,” the netherworlds of the Tibetan Buddhist afterlife—the beginnings of a theory that would coalesce into “The Psychedelic Experience: A Manual Based on the Tibetan Book of the Dead,” Leary and Alpert’s 1964 book with their Harvard collaborator Ralph Metzner. In 1965, Leary and Alpert went on a lecture tour, but it wasn’t until 1966, after several run-ins with the law, that Leary started earning his reputation as the “pied piper of LSD,” cultivating the media, saying things like, “To learn how to use your head, you have to go out of your mind,” and “Turn on, tune in, and drop out.” Many blame the federal ban on psychedelics, in 1970, at least in part, on the role Leary played in feeding a moral panic.

Ulrich’s selections, many of them previously unpublished, round out the trajectory of Leary’s life from professor to guru to fugitive to a nostalgic caricature of himself. The documents span Leary’s days at Harvard to his days as an Internet evangelist, when his aphorism became “the PC is the LSD of the nineteen-nineties.” (Messianic pronouncements came easily to him.) Ulrich concludes that if Leary had only “quietly conducted his drug studies at Harvard under controlled medical supervision, his story and that of the counterculture might have looked very different today.”

Ginsberg was pleased with the results of his experiments. He wrote in his January, 1961, trip report for Leary that “psilocybin seems to me to be some sort of psychic godsend.” He was not alone in wanting to re-create a mystical experience. As Oliver Sacks wrote in “Hallucinations,” published in 2012, “To live on a day-to-day basis is insufficient for human beings; we need to transcend, transport, escape; we need meaning, understanding, and explanation; we need to see overall patterns in our lives.” It is in large part because of their ability to offer such insights that LSD, psilocybin mushrooms, mescaline, ayahuasca, and other chemicals have retained a significant influence in American culture since their modern introduction, in the nineteen-fifties. The 1970 federal ban moved them underground. But, according to a 2010 survey, despite the laws that make such experimentation illegal, around thirty-two million Americans have tried LSD, mescaline, or magic mushrooms in their lifetimes.

For all the peer pressure I’d been taught to resist in public-school D.A.R.E. lessons, nobody invited me to drop acid as a high-school or college student. As a young adult living in Little Rock, Miami, and New York in the aughts, LSD did not factor into the casual drug use of my friends, who tended to use alcohol, marijuana, cocaine, or shared-out Adderall and Xanax prescriptions. (In the early two-thousands, a major federal bust greatly reduced the national supply, but I also didn’t try very hard to find it.) As Tao Lin writes in his new book, “Trip: Psychedelics, Alienation, and Change,” “I more than half-believed the stereotypes I’d absorbed throughout my life about psychedelic drugs—that they caused insanity and out-of-control behavior and were hazardous and uninteresting. People on psychedelics, when not going insane, seemed to laze or frolic or dance in fields and not worry or think about anything but only (somewhat pointlessly, I’d always felt) look at things, which they usually described as geometric.”

In “Trip,” Lin describes his life from 2012 to 2016, a time when he began a deliberate inquiry into psychedelics. Following the publication of his novel “Taipei,” in which the characters consume MDMA, Xanax, heroin, mushrooms, and more, and which Lin has said that he wrote using a “ ‘whatever it takes’ attitude regarding amphetamines and other drugs,” he attempted a shift from pharmaceutical to psychedelic drug use as part of a “sustained, conscious effort” to “not drift toward meaninglessness, depression, disempowering forms of resignation, and bleak ideologies like existentialism.” Lin’s eighth book is his first work of nonfiction—a mix of memoir, trip reports about substances like psilocybin, DMT, and salvia, and digressions on botany, health, and human evolution. Lin avoids writing in figurative language, and there is little hyperbole in these reports, nor references to nineteen-sixties-era acid metaphysics. “Trip” is, if not a guide to self-help, a book about a person trying to be happier, in part by changing the kinds of drugs he uses.

It is also a biography of the lecturer and writer Terence McKenna, whose discourses on psychedelics from the nineteen-eighties and nineteen-nineties have been preserved on YouTube since McKenna’s death, in 2000. McKenna, Lin writes, was against gurus, and disparaged the New Age self-help cults of his time. I listened to McKenna’s lectures on the recommendation of Lin, whom I met and befriended, in the summer of 2013, in the middle of my own experiments with psychedelic drugs, which I tried for the first time at the age of thirty-one. I spent that late summer and fall listening to McKenna’s lectures when I went running. He seemed to me, too, as Lin writes, “more earnest and sophisticated and undeluded than anyone I’d absorbed this much information from on nonmaterial topics like consciousness and imagination.” Not all of McKenna’s theories about language, evolution, psychedelics, and the acceleration of history were empirically provable, but it was relaxing to contemplate the cosmos via his droll jokes.