Three days later, on April 19, 1943 (known as Bicycle Day), Dr. Hofmann intentionally ingested 250 µg of LSD, which he hypothesized would be a threshold dose, based on other ergot alkaloids. In reality, this is a fairly substantial dose and the threshold would actually be around 25 µg. Hoffman wrote:
"By now it was already clear to me that LSD had been the cause of the remarkable experience of the previous Friday, for the altered perceptions were of the same type as before, only much more intense. I had to struggle to speak intelligibly. I asked my laboratory assistant, who was informed of the self-experiment, to escort me home. We went by bicycle, no automobile being available because of wartime restrictions on their use. On the way home, my condition began to assume threatening forms. Everything in my field of vision wavered and was distorted as if seen in a curved mirror. I also had the sensation of being unable to move from the spot. Nevertheless, my assistant later told me we had traveled very rapidly."
Dr. Hofmann summoned a doctor, who could find no abnormal physical symptoms other than extremely dilated pupils. After spending several hours terrified that his body had been possessed by a demon, that his next door neighbour was a witch, and that his furniture was threatening him, Dr. Hofmann feared he had become completely insane.