First synthesized by Albert Hofmann on November 16, 1938, LSD went on to become a staple of the psychedelic world and the centerpiece of the 1960s counterculture. On April 19, 1943, Hofmann returned to investigate LSD further and ingested 250 micrograms of LSD. Hofmann believed this dose to have a minuscule, threshold effect. He rode his bicycle home and later wrote that, "... little by little I could begin to enjoy the unprecedented colors and plays of shapes that persisted behind my closed eyes. Kaleidoscopic, fantastic images surged in on me, alternating, variegated, opening and then closing themselves in circles and spirals, exploding in colored fountains, rearranging and hybridizing themselves in constant flux ..." This day in history later became known as Bicycle Day and is celebrated by LSD enthusiasts as the world's first LSD trip.
Duration: 8-12 hours [Can be significantly longer with heroic doses]
Low dose: 50-100mcg
Medium (typical) dose: 100-250mcg
High dose: 250+mcg
Long term effects
At least one week for full effect due to rapid tolerance build, though it's generally advised to wait longer between trips. No more than once a month is advised, but this can vary from person to person.
Virtually none, save for choices you make under the influence.
LSD is known to bring out latent mental illness and should be avoided by those predisposed to said illnesses.