Bryon Gysin's Dreamachine is another one of his cool discoveries. The Dreamachine is simply a cylinder with slits on the slides, placed on a record turntable and rotated. The light bulb underneath the cylinder, illuminates through the slits and creates a visual stimuli. Behind closed eyes, the user will see all sorts of patterns, shapes, and colors, and might even enter a hypnagogic state. It can be pretty intense, but the experience is over as soon as the user opens their eyes.
to try it online: http://www.netliberty.net/dreamachine.html