"By this time, Schiller was a photojournalist of some renown, and with a batch of good-quality LSD finding its way into counterculture circles and talk of so-called Acid Tests–musical events fuelled by Kool-Aid laced with psychedelics–taking place along the west coast, he set out to document the new scene. Through acid guru Timothy Leary, Schiller made contact with Kesey, who told him the Pranksters were due to hold an Acid Test on Sunset Boulevard. Mid-trip, they skipped down the block to pose for portraits. 'Cassady was there,' Schiller recalls. 'At one point I went over, and he started dancing with his silhouette.'"
Louis Pattison in a 2011 Guardian article tells the backstory of the cover of the Flaming Lips album The Soft Bulletin.