We saw some small boys fiercely competing at a game of throwing shells into the sea. The game is to pick a shell from the shore which has been rubbed smooth by the waves. You hold the shell flat with your fingers, and stooping at an angle and low to the ground, you spin it over the waves as hard as possible, so that it may either strike once and glide smoothly across the sea's surface, or flash and leap as it skips again and again along the tips of the waves. The winner is the boy whose shell travels furthest, and skips the most times.
--Minucius Felix, Third Century AD