I remember reading an account in Omni magazine from Dr. John Lily of one of his experiences with LSD and a deprivation tank. He became a point of light, racing at ever higher speed through the cosmos. He reaches the edge of the universe, and two other points of light accost him and announce that they are the "Intergalactic Thought Police" and that he's not allowed to proceed further.

Dr. Lily inspired the movies "Altered States" and "The Day of the Dolphin."