One day, a cowboy was crossing the desert to do some trading and came upon an Indian. The Indian was laying on his back and had an erection that stuck straight up in the air.

The cowboy asked the Indian what he was doing.

The Indian replied, "Me tell-um time." This made sense to the cowboy, he was using his penis as a sundial.

A few days later, after completing his trading, the cowboy came across the same Indian. This time the Indian was laying on his back vigorously masturbating.

The cowboy asked what he was doing this time.

The Indian said, "Me wind-um watch."