The post chaise was a a closed four-wheel horse-drawn carriage designed for rapid long-distance travel. It seated two to four passengers, and had windows at both the sides and the front of the carriage. Because the driver rode one of the horses, the place where the driver's seat or 'box' would normally be was used as a luggage area.
Click here to see a photo of a post chaise.
(See also bookmark p.245)