Wasson's next major contribution was a study of the ancient Vedic intoxicant soma, which he hypothesized was based on the psychoactive fly agaric ("Amanita muscaria") mushroom. This hypothesis was published in 1967 under the title "Soma: Divine Mushroom of Immortality". His attention then turned to the Eleusinian Mysteries, the initiation ceremony of the ancient Greek cult of Demeter and Persephone. In "The Road to Eleusis: Unveiling the Secret of the Mysteries" (1978), co-authored with Albert Hofmann and Carl A. P. Ruck, it was proposed that the special potion "kykeon", a pivotal component of the ceremony, contained psychoactive ergoline alkaloids from the fungus Ergot ("Claviceps spp.").