We swear by the thunder powers, by the wakinyan. You tell a story and somebody doesn’t believe you, doubts your words.
Then you say, “Na ecel lila wakinyan agli—wakinyan namahon.” That settles it. Everyone knows then that you are telling nothing but the truth. Otherwise lightning would strike you dead. Likewise, if you swear by the sacred pipe, holding it in your hands, you cannot lie, or the thunder-beings will kill you.

Lame Deer-Seeker of Visions, p. 241