After read­ing a recent issue of Cor­tex, Mind Hacks goes into some detail dis­cussing the Ganzfeld pro­ce­dure:

The Ganzfeld pro­ce­dure exposes the par­tic­i­pant to ‘unstruc­tured’ sen­sa­tions usu­ally by plac­ing half ping-pong balls over the eyes so they can only see dif­fuse white light and by play­ing white noise through headphones.

It is prob­a­bly best known for its uses in para­psy­chol­ogy exper­i­ments, but it is also used to induce hal­lu­ci­na­tions and sen­sory dis­tor­tions which are much more likely to occur in the absence of clearly defined sen­sory experiences.

The post goes on to vividly describes some hal­lu­ci­na­tions before let­ting us know how we can try this at home.