From the Navaho, The Wanderings

After the Four First Beings started for the East, First Woman turned back and said: "When I wish to do so, I will send chest colds and disease among the people; when I wish to do so I will send death, and the sign will be the coyote." (The old men say that when a coyote howls many people cough. The belief is current that certain appearances of a coyote foretell death.)

So the Four First Ones went East and they took all their powers with them.

The Sun spoke again: "When anyone thinks he sees me, he will see me because it will mean that there is an enemy in the country. The people will suffer from enemies." And the Sun returned to his home and he took all his powers with him.

And Hasjelti and all of his Holy People said: "If anyone sees us it will also be a sign that an enemy is coming into the country. If he hears us call, that same person will be killed by an enemy before the day is over." And so saying, they all returned to their homes and all their powers went with them. They were never seen again. (Now, if anyone thinks he sees one of the Holy Beings, it will not be for the good of the people. It is considered a bad omen.)