The black circle under the tray is a sofra. Source: The Bremen album, 1574
A round leather or cloth laid down to catch crumbs while eating–essential in a world where any civilized floor was carpeted. Often a sofra had a drawstring around the edge so it could be picked up and carried outside to be shook out without dropping crumbs in the process.
Low tables didn’t come into use until the late 16th century. Before then, the sofra was the only “tabletop” people dined from.