A psilocybin mushroom is one of a polyphyletic group of fungi that contain any of various psychedelic compounds, including psilocybin, psilocin, and baeocystin. Common, colloquial terms for psilocybin mushrooms include psychedelic mushrooms, magic mushrooms, shrooms, and mush.
This fungus contains chemicals similar to those used in the synthetic psychedelic drug LSD. Convulsive ergotism causes a variety of symptoms, including nervous dysfunction.
Leary's psychedelic experiments are part of hippie lore, but the man who did the most to bring magic mushrooms to mainstream U.S. drug culture was a writer and ethnobotanist named Terence McKenna.