Bicycle Day marks the advent of the first human controlled experimentation with the potent hallucinogen and psychedelic drug LSD. It is held by some as a celebration of LSD, its inventor Albert Hofmann, and the psychedelic culture which the drug is inextricably associated.
While working for Sandoz Laboratories, Dr. Albert Hofmann (1906 - 2008) developed and characterized a number of derivatives of the active compounds found in the Ergot fungus as potential therapeutic agents, one of which was lysergic acid diethylamide-25 (LSD). In the original research on LSD Hofmann and colleagues had noted erratic behavior in rodents treated with the drug but the significance of this was not immediately obvious. On April 16th 1943 Hofmann unknowingly and accidentally ingested a small and unknown quantity of the drug, resulting in unexpected, astounding and terrifying hallucinations. The experience prompted Hofmann to conduct a controlled self-trial of LSD.
On April 19th 1943, Hofmann intentionally ingested 250 g of LSD in order to characterize the drug's psychoactive effects. He had speculated that 250 g would be a conservative dose, as it this point the remarkable potency of the drug was unknown. Approximately an hour after consumption Hofmann was feeling the effects of the drug and requested that a lab assistant escort him home. Due to wartime restrictions on the use of motor vehicles this "trip" was made by bicycle (hence the name "Bicycle Day").
Hofmann's experiences on Bicycle Day and a general history of LSD are recounted in more detail in his book, LSD - My Problem Child.
Related threads and videos:
Happy Bicycle Day everyone!
Bicycle Day - animation by David Normal to mark Albert Hofmann's centenary celebration
A Bicycle Trip - short animated film