Simplify the following text for a Grade 9 native English-speaking person.
Original: 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 .
Simplified: Speakers at the rally included Timothy Leary , Richard Alpert ( soon to be more widely known as ` Ram Dass ' ) , and poets like Allen Ginsberg , who chanted mantras , and Gary Snyder . Leary set the tone that afternoon with his famous phrase `` Turn On , Tune In , Drop Out '' .