90:1.4
But not all shamans were self-deceived; many were shrewd and able tricksters. As the profession developed, a novice was required to serve an apprenticeship of ten years of hardship and self-denial to qualify as a medicine man. The shamans developed a professional mode of dress and affected a mysterious conduct. They frequently employed drugs to induce certain physical states which would impress and mystify the tribesmen. Sleight-of-hand feats were regarded as supernatural by the common folk, and ventriloquism was first used by shrewd priests. Many of the olden shamans unwittingly stumbled onto hypnotism; others induced autohypnosis by prolonged staring at their navels.