Namkhai Norbu Rainbow body of Ugyen Tendzin (PDF)

Tibetan Buddhism is the only religion which has developed an advanced meditation in the practitioners at the end of life tells his students to leave him alone in a room or tent of about seven days and then takes the meditation position. When the students who have surrounded the room praying night and day, finally enter the room they find only the practitioner's robe and sometimes fingernails and some hair.

This practice is called Rainbow Body (Tib. jalu) and is proof that the practitioner has mastery over the physical elements. Namkhai Norbu Rinpoche in this book recounts in detail the life of his uncle and his passing away in rainbow body.