Dark retreat
Dark retreat (Wylie: mun mtshams) is a spiritual retreat in a space that is completely absent of light, which is an advanced practice of Tibetan Buddhism and Bön. == Overview == The dark retreat environment of the Bon religion is particularly conducive to the practice of certain visionary yogas (such as the “six-limbed yoga” of Kalacakra and the Dzogchen practice of Thögal for the attainment of the Rainbow Body), which according to Hatchell are "techniques that lead to the experience of spontaneously arising visual experiences, which are said to occur without deliberate effort or conceptual imagination, and which appear before the practitioner’s eyes." According Hatchell, the Kalacakra system's six yogas:instruct the yogi to spend lengthy periods either gazing at the blank sky or residing in a dark room specially prepared to seal out all light.