On the top of the wall lay a structure of burnt brick, about a foot and a half in height, under the tiles and projecting like a coping.... when the tiles on the roof are broken or thrown down by the wind so that rain-water can leak through, this burnt brick coating will prevent the crude brick from being damaged, and the cornice-like projection will throw off the drops beyond the vertical face, and thus the walls, though of crude brick structure, will be preserved intact.

Chapter VIII, Sec. 18 - De architectura (The Ten Books On Architecture) (~ 15BC) - Book II