In ancient Greece, baby potties doubled as baby chairs, on this wine jug, or chous, from the 5th century bce, the baby is playing with a rattle.

At the bottom of a cup a woman interacts with a baby in a potty chair.

And on this oil jug, a woman stands next to a baby (this time clothed) in a potty chair.

The potties have a hole in the seat, and from the back or under the base there is a space for a pot to collect waste. There are handles to move the chair, and the wide base and holes for securing the chair with rope add safety. 

The potties needed to fit the baby: this baby, at six months old (and diapered) found it too snug. But in 1984, when tested with another, smaller, six-month-old (unclothed)—she immediately put it to use.

Sources:

The British Museum.

The Fitzwilliam Museum.

Lynch, Kathleen M. and John K. Papadopoulos. Spring 2006. “Sella Cacatoria: A Study of the Potty in Archaic and Classical Athens.” Hesperia: the Journal of the American School of Classical Studies at Athens, 75(1) pg 1-32.