... Mystics Under the Microscope. (Hat tip, Dave Lull.)
For what it's worth, this is pretty much in accord with my own experiences. Psilocybin was my favorite hallucinogen, and I took it usually in its natural form: mushrooms. (Just for the record, I experimented with these sorts of things for about 20 years, from about 1969 to 1989; in 1989 I went straight for good.) Anyway, I liked shrooms the best because the high seemed more natural (there was always something inorganic about the LSD experience), and there is no doubt that set and setting are crucial, and that one tends to interpret - or even have - the experience in terms of the religious tradition one is most familiar with. I certainly have come to think that all the great religions are takes on the same transcendent dimension of being (if I can put it so) from different angles of approach.