"...The Human Be-In was announced on the cover of the fifth issue of the San Francisco Oracle as "A Gathering of the Tribes for a Human Be-In." The occasion was a new California law banning the use of the psychedelic drug, LSD that had come into effect on October 6, 1966.[5] The speakers at the rally were all invited by Bowen, the main organizer. They included Timothy Leary in his first San Francisco appearance, who set the tone that afternoon with his famous phrase "Turn on, tune in, drop out" and Richard Alpert (soon to be more widely known as 'Ram Dass'), and poets like Allen Ginsberg, who chanted mantras, and Gary Snyder. Other counterculture gurus included comedian Dick Gregory, Lenore Kandel, and Jerry Rubin. The Hells Angels, at the peak of their 'outlaw' reputation, corralled lost children. Music was provided by a host of local rock bands including Jefferson Airplane, The Grateful Dead and Quicksilver Messenger Service, who had been staples of the Fillmore and the Avalon Ballroom since February 1966, and 'underground chemist' Owsley Stanley provided massive amounts of his "White Lightning" LSD, specially produced for the event, to the gathered masses.
If HTML was there at the time, the day may have looked a bit like this: