While working at the mental hospital that inspired his novel One Flew Over the Cuckoo’s Nest, Ken Kesey became one of the first Americans to take LSD. You can relive his historic experience, thanks to the psychedelic clip above from Alex Gibney’s new documentary, Magic Trip.

Doctors asked Kesey to participate in clinical research documenting the drug’s mind-melting capabilities in 1960. They sequestered him in a room with a tape recorder and an attendant, and Kesey offered play by play on hallucinations that included talking frogs, mummies and a Wollensak tape recorder that suddenly seemed to sprout a beard.

The audio tapes were discovered decades later in an Oregon barn by filmmaker Gibney. As seen in the exclusive clip above from Magic Trip, Gibney and co-director Alison Ellwood re-enacted the historic drug test with trippy sequences animated by the Imaginary Forces studio.

Magic Trip follows Kesey’s adventures, including leading a band of LSD-taking Merry Pranksters across the country in a converted school bus, staging acid-drenched happenings with the Grateful Dead.

Toward the end of his rambling commentary in the clip above, Kesey hints at his future role as psychotropic evangelist: “I felt like I discovered a hole in the center of the Earth and you could see jewelry down there, and you wanted other people to go down there and enjoy it.”

Magic Trip, rated R, opens Friday in select theaters. You can watch the movie on demand now.