R. Gordon Wasson, Albert Hofmann, and Carl Ruck formally proposed 'entheogen' ('generating the divine within') in The Road to Eleusis (1978), arguing the Eleusinian kykeon was an ergot preparation. Wasson's Soma: Divine Mushroom of Immortality (1968) identified the Rigveda's soma with Amanita muscaria; his 1957 Life magazine essay on Maria Sabina's Mazatec mushroom velada launched the Western mushroom era. The Rigveda's soma hymns (Book 8) are the primary Sanskrit witnesses.
Modern clinical trials, Johns Hopkins psilocybin studies from 2006 onward, measure 'mystical-type experience' with questionnaires, quietly validating what the rituals always claimed while bracketing the theology. The ritual container, set and setting, is the part science now prescribes.
The Rigveda does not describe soma as a symbol of the divine; it calls soma a god, pressed, filtered, and drunk. The entheogenic thesis holds that several religions were founded on chemistry, making the oldest question in the field not theological but botanical.
If a sacrament and a controlled substance can be the same molecule, who decides which it is?