The Byrds: Eight Miles High

Released in 1966 and, says Wikipedia, influenced by Ravi Shankar and John Coltrane,Eight Miles High was influential in developing psychedelic rock, raga rock and psychedelic pop.

Critics - and this is still Wikipedia talking - often cite it as the first psychedelic rock song.

I would only add that, while this single version lasts just three and a half minutes, there are any number of live performances online that last several days.