Albert Hofmann stumbled onto the effects of LSD

On April 16, 1943, the Swiss chemist Albert Hofmann was purifying a batch of lysergic acid diethylamide (LSD-25) at Sandoz Laboratories in Basel. He had first synthesized the compound five years earlier while screening derivatives of ergot, a fungus that grows on rye, and had since shelved it.

That afternoon he was overcome by a peculiar dizziness and restlessness and had to stop work. Having apparently absorbed a trace through his fingertips, he went home, lay down, and watched “an uninterrupted stream of fantastic pictures” with intense, kaleidoscopic color.

Three days later he deliberately swallowed 250 micrograms, a dose he assumed was tiny — and endured a far more harrowing trip.

That second, intentional experiment on April 19 is now remembered as “Bicycle Day,” after the wobbling ride home he took as the drug peaked. Hofmann lived to 102, calling the substance his “problem child.”