 In his most famous paper, “On Travels in the Universe of the Soul”, he reports on self experimentation using lysergic acid diethylamide (LSD) and psilocybin conducted with his friends Dr. Albert Hofmann, pharmacologist Professor Heribert Konzett, and writer Ernst Jünger.He would later publish a book in 1966 that was in greater reference to these self experiments called, “Vom Rausch im Orient und Okzident” ("On Inebriation in the East and the West").Later Dr. Gelpke would return to Switzerland, where he suffered from a stroke, dying at age of 43.