Aldous Huxley
His 1954 account is the actual origin point of the modern equation between psychedelics and mysticism — a claim usually attributed to later, more famous names in psychedelic research, all of whom wrote after him.
Aldous Huxley, The Doors of Perception (1954), under Humphry Osmond's supervision
English novelist who took mescaline under clinical supervision in 1953 and argued in print that the drug state and the mystical state are the same experience.