Below is an excerpt from Joseph Campbell's 1988 THE INNER REACHES OF OUTER SPACE, pages 90 and 152 (for the footnotes):
In the 1950s R. Gordon Wasson's investigations of the Mexican pre-Columbian mushroom cult (in collaboration with Albert Hofmann, the Swiss chemist renowned for his discovery of LSD in 1943) established beyond question the prominence of hallucinogens in the religious exercises of the whole Mayan-Aztec culture field. The same investigators in conjunction with the classicist, Carl A.P. Ruck, have lately revealed the likelihood of the influence of a hallucinogen (ergot of barley) in the Greek mysteries of Eleusis.[*]
Already in 1968, Wasson published his disclosure of the mysterious Vedic sacramental, Soma, as probably a product of the mushroom AMANITA MUSCARIA (fly agaric)[*] Aldous Huxley's THE DOORS OF PERCEPTION (1954), describing his own visionary experiences under the influence of mescaline, opened the way to a popular appreciation of the ability of hallucinogens to render perceptions of a quasi, or even truly, mystical profundity. There can be no doubt today that through the use of such sacramentals, revelations indistinguishable from some of those reported of yoga have been experienced. Nor can there be any doubt that the source of the revelations is the psyche of the practitioner--the unconscious, that is to say. They are revelations, that is to say further, of the archetypes of the collective unconscious, elementary ideas A PRIORI of the species HOMO SAPIENS SAPIENS, such as may appear spontaneously no matter where. ...
* R. Gordon Wasson, Albert Hofmann, and Carl A.P. Ruck, THE ROAD TO ELEUSIS: UNVEILING THE SECRET OF THE MYSTERIES (New York: Harcourt, Brace, Jovanovich, 1978).
* R. Gordon Wasson, SOMA: DIVINE MUSHROOM OF IMMORTALITY (New York: Harcourt, Brace, 1968).