Direct transcendence (thod rgal), together with Breakthrough (khregs chod) contemplation, constitutes the two primary contemplative traditions of the Seminal Heart (snying thig) subtradition of the Great Perfection (rdzogs chen) tradition within the Nyingma (rnying ma) school of Tibetan Buddhism. Direct transcendence meditation involves an innovative cultivation of spontaneous visions through the use of disciplined postures, gazes, and breathing patterns while staring into the sky, typically off to the side of the sun. There are also variants that can be done in pitch blackness within specially prepared dark houses (mun khang). The practice is described as involving spontaneous eruptions of light in diverse patterns, colors, and ultimately iconographic forms that increase in size, complexity, and detail through a series of phases summarized into "four visions" (snang ba bzhi). Ultimately the visions take the form of maṇḍalas of Buddhas constituting pure lands, which pervade the entire sky, before in the culminating vision they fade away into the infinite reaches of an empty sky, making the moment of enlightenment.
An Essay on the Tibetan Term Thod rgal