Psychonautnov. verb.— One who "trips" or embarks on shamanic odysseys of discovery in the universe of the mind; a mental voyager. Hence: Psychonautic nov. verb., Psychonautical nov. verb.
1970 Jünger Annäherungen, 430. Psychonauten [Psychonauts] [chapter title]
1989 Siegel Intoxication, 14. I trained a group of human subjects—the media [sic] dubbed them psychonauts—to take controlled trips with LSD and other drugs...
1970 Ott Ayahuasca Analogues, 98. A self-experimenter like Heffter was later aptly characterized by famed German writer Ernst Jünger, in his logbook of personal drug experimentation... as a psychonaut, a voyager employing entheogenic drugs as his vehicle.
1995 Anon. Altrove, 2: 25. Attualmente, il termine "psiconauta" ha subito una nuova connotazione, potendo anche designare un particolare tipo di psiconauta psichedelico: il ricercatore di nuovi composti o intrugli psicoattivi. [Presently, the term "psychonaut" has acquired a new connotation, used also to designate a particular type of psychedelic psychonaut: the researcher of new compounds or psychoactive principles.]
Source:The Age of Entheogens & The Angel's Dictionary
by Jonathan Ott