sorry Hombre, but i tend to disagree. eight miles high was written after eight days a week, the byrds went out of their way and copied the beatles just like everyone else did in those days. i'm not saying that's a bad thing.. as for the origins of psychedelia, beyond that that term is poorly defined... i would look to the folk rock and acid rock bands out of san franscisco during that time frame, think about the free speech movement and flower power.
Of course, I agree that the Byrds were influenced by the Beatles, even in that groundbreaking song. But the way "Eight Miles High" was recorded and played was very innovative, something the Beatles hadn't done yet.
About the origin of pychedelia, we could also name "The Word", because of the colorful lyrics, the repetitive guitar, crazy bass playing, the intrincate drumming and the hypnotic harmonium. But it would be a proto-psychedelic tune. But still the first nearly pure psychedelic songs I can think of are "Eight Miles High" and "Shapes Of Things".
As for everyone copying the Beatles, I think it was a reciprocal thing. The Beatles influenced others as others influenced the Beatles as well (Dylan, Byrds, Yardbirds, Beach Boys, etc.). As John said, the Beatles were a part of the 60's movement, not the whole movement.