Trigon was a ball game played by the ancient Romans. It probably involved three players standing in a triangle (hence the name) and passing a hard ball back and forth, catching with the right and throwing with the left hand. Besides the three players, called trigonali, there were also assistants called pilecripi, who kept score and retrieved runaway balls.
Petronius's Satyricon has a description of a ball game usually assumed to be trigon, although its name is never mentioned. The bald old man Trimalchio is playing with a couple of young curly-haired slave boys. Trimalchio is obviously not a serious trigon player because he plays in his sandals, and he never stoops to retrieve the ball but instead has a servant replace it with a fresh ball from a big sack. When he snapped his fingers, a slave brought him water to wash his hands, and when he was finished he dried his hands with the long curly hair of the young slave boys.
Petronius also remarks that in this case, the pilecripus did not count the number of times the players successfully passed the ball, but instead the number of balls that dropped on the ground. This may be a joke making fun of Trimalchio's low level of skill, or simply an innovative scoring method.