Among those who follow the spirit there are some who have pierced the veil of appearances through fasting, sweat lodges, pipe ceremonies, prayers and offerings, and through dreams. "Sitting in your chair and going somewhere" is yet another way that some native people have pierced the veil. Those who have encountered the spirit world sometimes tell of visions of the past or future which prove true, or of prayers which affect future events, or perhaps even past ones!

Evan T. Pritchard, No Word for Time