Ethnomycologist and banker Wasson provided evidence for the important role that hallucinogenic mushrooms - in particular the ubiquitous mushroom Amanita muscaria (fly agaric) - play in various ancient and modern cultures. The first edition was limited to 680 copies finely printed at the Stamperia Valdonegga in Verona.  Digital facsimile of the trade edition issued by Harcourt Brace Jovanovich from the Internet Archive at this link.

Argues that the psycho-active ingredient in the secret kykeion potion used in the Eleusinian mysteries was most likely the ergotism causing fungus Claviceps purpurea. Furthermore the book introduced the term "entheogen" as an alternative for terms such as "psychedelic", "hallucinogen" and "drug" that can be misleading in certain contexts.