singularity

If one is able to cultivate the contemplation of the white bones and see even a single one of the three hundred and sixty bones, and if later one does not commit any evil deeds, then after death one will go straight to Tuá¹£ita heaven. How much more so one who successfully [sees] his entire skeleton!

meditator’s journey is not psychological but visionary.

sees a great bright light shining from the crown of his skull. It looks like a flame the size of a spear in length and thickness. It emerges from the crown of the skull and then reverses itself so that it points downward and reenters through the crown of the skull. Passing through the crown of the skull, it enters his neck bone. Emerging from his neck bone, it enters his chest bone. Emerging from his chest bone, it enters his navel. Emerging from his navel, it enters his coccyx. After entering his coccyx, it disappears. With its disappearance, there immediately appears a spontaneously arising great cloud of light.It is adorned with jewels and pure jewel-flowers more exquisite than all other material forms. Within the cloud is a buddha named Śākyamuni, replete in radiance, endowed with the thirty-two major and eighty minor marks, each one radiating a thousand lights. These lights are extremely bright, blazing forth like a hundred thousand million suns. This buddha preaches the teaching of the four truths. His light dazzling, he stands  before the practitioner and lays his hand upon his head. (Chan Essentials 2.20.9–10)