watermark
n.
A design in paper, formed by a difference in amount of fiber, that is visible when viewed by transmitted light.
Notes
Watermarks may be either lighter or darker than the surrounding area, depending on the manner in which they are made.
Citations
Roberts and Etherington 1982 Forms of the watermark are generally divided into four very broad classes: 1) the very earliest, generally consisting of simple circles, crosses, knots, ovals, three-hill symbols, triangles, and the like, which were easy to construct simply by twisting and bending soft wires. (These early marks also included many pomme crosses, based on the Greek cross with balls or circles at the ends of the cross bars. A similar watermark, found on Italian paper of the 14th century, consists of a circle above which is a patriarchal or papal cross. These earliest marks were prevalent from about 1282 to 1425); 2) watermarks emphasizing man and his works. (Thousands of designs of this nature have been noted, a large number of them featuring human hands in various forms); 3) watermarks consisting of flowers, fruit, grains, trees and other plants, etc.; and 4) watermarks consisting of wild, domesticated, and legendary animals.