Stand on one shore of a stream. Bow your head, chin against your chest. Hold your hand to your forehead in a salute. Move your hand down until the front edge of it seems to touch the opposite shore. Without changing the position of your hand, make a quarter turn. Notice the point at which the edge of your hand seems to touch the near shore. Pace off the distance to that point, and you will know the width of the river. Napoleon might have used the brim of this hat instead of his hand. If you are wearing a cap with a visor, so can you.