Newly added to the Resources page:
“Poisonous Mushrooms Used in Ur-Orgies” – a chapter from Scatalogic Rites of All Nations by John G. Bourke, 1891 (PDF of scanned pages from book, uploaded to this site)
Despite its age, this piece of writing is actually pretty useful. He includes tons of quotes from older sources that are now not easily accessed. A lot of direct information from Siberia.