At that time, the Roman Rite required the use of three altar cloths, to which a cere cloth, not classified as an altar cloth, was generally added. This was a piece of heavy linen treated with wax ("cera", from which "cere" is derived, is the Latin word for "wax") to protect the altar linens from the dampness of a stone altar, and also to prevent the altar from being stained by any wine that may be spilled. It was exactly the same size as the "mensa" (the flat rectangular top of the altar).