The Sacred Mushroom and the Cross

This book by John Marco Allegro has come up 2 times on Joe Rogan. 2 of those mentions were genuine on-air recommendations, not just passing references. The people who brought it up: Joe Rogan. Every occurrence below links to the episode page and to the exact second it was said on YouTube.

The book relates the development of language to the development of myths, religions, and cultic practices in world cultures. Allegro argues, through etymology, that the roots of Christianity, and many other religions, lay in fertility cults, and that cult practices, such as ingesting visionary plants to perceive the mind of God, persisted into the early Christian era, and to some unspecified extent into the 13th century with reoccurrences in the 18th century and mid-20th century, as he interprets the fresco of the Plaincourault Chapel to be an accurate depiction of the ritual ingestion of Amanita muscaria as the Eucharist.