I once asked a young chief what he considered the height of a lofty pine.

It was in the afternoon, about three o'clock.

He walked to the end of the shadow thrown by the pine-tree, and fixed his arrow in the ground, measured the length of the arrow, and then the length of the shadow thrown by it; then measuring the shadow of the pine, he deducted from it in the same proportion as the difference between the length of the arrow, and the length of its shadow, and gave me the result.

He worked the Rule of Three without knowing it.
But the most remarkable instance occurred when we were about to cross a wide and rapid river, and required a rope to be thrown across, as a stay to the men and horses.

The question was, what was the length of the rope required; _i.e._, what was the width of the river?
An old chief stepped his horse forward, to solve the problem, and he did it as follows:--He went down to the side of the river, and fixed upon a spot as the centre; then he selected two trees, on the right and left, on the other side, as near as his eye could measure equidistant from where he stood.