Practitioners who have realized emptiness can, on entering the state of emptiness, step on a stone as if on clay and leave behind clear footprints. However, prior to realizing emptiness, they are like ordinary people; the stone under the feet feels just as hard.

There is this description in Khenpo Ngachung’s biography: once when he was waving the vajra and bell, he carelessly dropped them on a stone. When they landed, the stone suddenly became as soft as butter. The vajra and bell formed a clear impression on the stone; an image of the stone was also clearly etched on the vajra and bell. In many monasteries in Tibet, a lot of masters left behind similar footprints and handprints.

- Quote from The Logic of Emptiness,"Seeing All External Objects as Phenomena of the Mind"