Psychedelic Drugs Reconsidered

"... a psychedelic drug is one which, without causing psychical addiction, craving, major psysiological disturbances, delirium, disorientation, or amnesia, mor or less reliably produces thought, mood, and perceptual changes otherwise rarely experienced except in dreams, comtemplative and religious exaltation, flashes of vivid involuntary memory and acute psychoses. "

Lester Grinspoon and James B. Bakalar - Psychedelic Drugs Reconsidered