Ken Kesey and his Merry Pranksters helped shape the developing character of the 1960s counterculture when they embarked on a cross-country voyage during the summer of 1964 in a psychedelic school bus named "Furthur." Beginning in 1959, Kesey had volunteered as a research subject for medical trials financed by the CIA's "MK ULTRA" project. These trials tested the effects of LSD, psilocybin, mescaline, and other psychedelic drugs. After the medical trials, Kesey continued experimenting on his own, and involved many close friends; collectively they became known as "The Merry Pranksters." The Pranksters visited Harvard LSD proponent Timothy Leary at his Millbrook, New York retreat, and experimentation with LSD and other psychedelic drugs, primarily as a means for internal reflection and personal growth, became a constant during the Prankster trip.