The analysis of twenty species from seven genera of Pacific Northwest mushrooms revealed psilocybin (and in some cases psilocin as well) in seven species from three genera. The species found to contain psilocybin (and psilocin) varied from one collection to another by more than a factor of seven in amount present. Total psilocybin and psilocin levels in species known to be in use for recreational and entheogenic purposes varied from 0.1% by dry weight up to a high of nearly 2% by dry weight.
Beug, M. W., & Bigwood, J. (1982). Psilocybin and psilocin levels in twenty species from seven genera of wild mushrooms in the Pacific Northwest, U.S.A. J Ethnopharmacol, 5(3), 271-285. doi:10.1016/0378-8741(82)90013-7