§ 8 Of Transparent Marbles for Filling Window Openings
Some sorts of marble are found in Greece and in all parts of the East, which are white and yellowish, and very transparent. These were used by the ancients for baths and hot-air chambers and for all those places which need protection against wind, and in our own days there are still to be seen in the tribune of San Miniato a Monte, the abode of the monks of Monte Oliveto, above the gates of Florence, some windows of this marble, which admit light but not air.51 By means of this invention people gave light to their dwellings and kept out the cold.