Wakan’taka told the Thunders to teach the medicinemen the specifics to use for each part of the body and never to use any others. A large stone, powdery and white within but sparkling on the outside, is considered a powerful medicine. Wakan’taka made only a few such stones and it is difficult to find them. He did not wish them to be used wantonly. Wakan’taka instructed the Thunders to tell the medicinemen to use this when all other medicines failed. It is good for any ailment. Some Indians keep it now. It is too wakan to use publicly.

The Canadian Dakota, p. 82