Tomorrow Never Knows is a song about meditation. It was adapted from 'The Tibetan Book of the Dead' By an acid tripping Lennon.George says in the anthology that he wasn't sure if John knew he was singing about meditation when he recorded the song.
I chose Tommorow Never Knows but Rain would be a close 2nd.
I thought the song was called Blue Jay Way. For second I thought there may be a beatles song I dont know