"there is an exercise called zazen - similar, I think, to the Theravadic practice of vipassana"

Zazen is a form of meditation central to Zen Buddhism, the aim of which is simply sitting, centering the self in the present. Theravada is the oldest surviving school of Buddhism, thought to be closest to the early form of this religion; vipassana is therefore one of the oldest techniques of meditation, a form which seeks insight into the nature of reality.