Carlos Castaneda (1925 - 1998) wrote a series of books (listed below) in which he purports to document his sorceror's apprenticeship to "Man of Knowledge" Juan Matus ("don Juan"), a Yaqui Native American. As part of his apprenticeship, Castaneda claimed to have prepared and consumed three hallucinogenic plants: Lophophora williamsii (peyote cactus, "Mescalito"), Psilocybin mexicana (magic mushrooms, "little smoke") and Datura innoxia ("devil's weed"). For the first book, The Teachings of Don Juan, he was awarded a bachelor's degree from U.C.L.A, and for the third book, Journey to Ixtlan, he was awarded a doctorate, also from U.C.L.A.
The problem is, the books were almost certainly entirely fictional. None of the events in the books have been independently corroborated, none of the people in the books have been identified, and Castaneda has stubbornly refused to provide any proof for the events depicted in the books. To some extent, this is understandable; if Matus indeed existed, I'm sure he would not want to have been overrun by the drug-addled freaks who certainly would have tried to seek him out.
But then stories began to emerge of Castaneda's Los Angeles cult: the financial, emotional, and sexual manipulation of his followers. After Castaneda's death, five of his followers vanished; the car, and later the corpse, of one of these followers was found in Death Valley.
I read these books in my early twenties, and was enchanted by them, but I questioned their veracity almost from the first page. My main bone of contention was that the hallucinogenic experiences described in the books were utterly unlike my own.