These are "Coach Pots" or "Bourdaloues".
They are also sometimes called "Banquet","Crinoline", "Ball" or "Sermon Pots".
They originated in France during the reign of Louis XIV.
It seems the court priest, Louis Bourdaloues was known for his hours-long sermons.
And of course, everyone who was in court was expected to attend his services.
The ladies, arrayed in elaborate dresses and petticoats, could not exit to use the facilities without causing a noticeable disturbance, so the use of these little porcelain pots came into use.
Thank heavens for discreet ladies' maids.
Today, these little pots command very high prices at antique sales and auctions.
In all the museums I've visited I have never seen one. But then, of course, they were not made over a long period of time. The one pictured at the left was manufactured in England.