There is an interesting occurence where certain spiritual practitioners who attained advanced level of realisation dissolving their bodies into light at death or even transcending physical death.
From my findings there are practitioners from Buddhism, Bon and Taoism who attained this kind of realisation.. however there may be others from other traditions as well... but I could not ascertain.
In the Tibetan traditions, Rainbow Body attainers can be from Bon or Buddhist Dzogchen strand of Practitioners. According to my finding, the Bon strand of Dzogchen originated from an Enlightened Being that predated the current era of Buddhism. It is said that the Bon Dzogchen is at least 15 000 years old.
In Taoism, there is sparodic accounts of Rainbow body occurence as well. In fact, there is a mountain in China that is named after such a person where his body dissappeared.
Here are useful and interesting links related to this amazing subject:
Recent Rainbow Body Attainers