Proposed by Wasson, Hofmann and Ruck in 1978. It would explain how an experience initiates consistently described as overwhelming could be produced reliably for thousands of people on a schedule. But no ancient source describes anything of the kind, the water extraction needed to separate soluble from toxic alkaloids is delicate, and the argument reasons backwards from the reported effect to a cause that would account for it.
What would resolve this Residue analysis of vessels securely associated with the Eleusinian rite, or a text that describes the preparation. Absent either, the question may be permanently undecidable, since the Mysteries were kept for roughly two thousand years and the secret held.
OpenClassics, ancient history, archaeochemistry, mycologyR. Gordon Wasson, Albert Hofmann and Carl A. P. Ruck, The Road to Eleusis: Unveiling the Secret of the Mysteries