back in the days of mushroom and acid, i had a plastic "cosmic window", which was two black and white patterns like above, with the white of the top layer transparent. a motor would spin the top layer over the lower.

the effect was like the above, except the fuzzy black balls would grow and shrink in time to the cycle, creating an in-out pulsing effect.

even without tripping, i wish i still had that for its effect as a meditative aid.