academics and medical professionals, who became acquainted with LSD in their work, began using it themselves and sharing it with friends and associates. Among the first to do so was British psychiatrist Humphry Osmond. Psychedelic subculture goes mainstream LSD historian Jay Stevens, author of the 1987 book Storming Heaven: LSD and the American Dream, has said that in the early days of its recreational use, LSD users (who were at that time mostly academics and medical professionals) fell into two broadly delineated groups. The first group, which was essentially conservative and exemplified by Aldous Huxley, felt that LSD was too powerful and too dangerous to allow its immediate and widespread introduction, and that its use ought to be restricted to the 'elite' members of society—artists, writers, scientists—who could mediate its gradual distribution throughout society. The second and more radical group, typified by Richard Alpert and Timothy Leary, felt that LSD had the power to revolutionize society and that it should be spread as widely as possible and be available to all. During the 1960s, this second 'group' of casual LSD users evolved and expanded into a subculture that extolled the mystical and religious symbolism often engendered by the drug's powerful effects, and advocated its use as a method of raising consciousness. The personalities associated with the subculture included spiritual gurus such as Dr. Timothy Leary and psychedelic rock musicians such as the Grateful Dead, Jimi Hendrix, Pink Floyd, Jefferson Airplane and the Beatles, and soon attracted a great deal of publicity, generating further interest in LSD. The popularization of LSD outside of the medical world was hastened when individuals such as author Ken Kesey participated in drug trials and liked what they saw. Tom Wolfe wrote a widely read account of the early days of LSD's entrance into the non-academic world in his book The Electric Kool Aid Acid Test, which documented the cross-country, acid-fueled voyage of Kesey and the Merry Pranksters on the psychedelic bus "Furthur" and the Pranksters' later 'Acid Test' LSD parties. In 1965, Sandoz laboratories stopped its still legal shipments of LSD to the United States for research and psychiatric use, after a request from the U.S. government concerned about its use. By April 1966, LSD use had become so widespread that Time magazine warned about its dangers. In December 1966, the exploitation film Hallucination Generation was released. This was followed by the films The Trip