Early unicycle?

In fact, the poor chap, called 10-Dog, is the unfortunate nephew of famed Mixtec ruler 8-Deer (whose exploits are chronicled in the Codex), and is depicted not on a unicycle but standing atop a temalácatl or sacrificial stone: in traditionally unequal gladiatorial style he’s fighting - armed just with a couple of short sticks - against two heavily armed jaguar warriors, one of whom (on the right) is 8-Deer himself. He’s hindered further by being tied by a rope from the centre of the stone to his waist. The scene is part of a description of a 12th century power struggle between two Mixtec city-states, Tilangtongo and Place of the Death Bundle of Xipe (Totec). The final outcome is the victory of 8-Deer as ruler of the whole Mixteca region. The sacrifice of 10-Dog is dedicated to the god Xipe Totec - you can see 10-Dog is wearing some of Xipe’s characteristic adornments, such as a conical hat and small waistcoat.

‘Riding’ a sacrificial stone used in gladiatorial rituals