On Architecture

9. Just as a silver mirror that is formed of a thin plate reflects indistinctly and with a feeble light, while one that is substantially made can take on a very high polish, and reflects a brilliant and distinct image when one looks therein, so it is with stucco. When the stuff of which it is formed is thin, it not only cracks but also soon fades; when, however, it has a solid foundation of sand mortar

and of marble, thickly and compactly applied, it is not only brilliant after being subjected to repeated polishings, but also reflects from its surface a clear image of the beholder.