law of diminishing returns. A concept in economics that if one factor of production (number of workers, for example) is increased while other factors (machines and workspace, for example) are held constant, the output per unit of the variable factor will eventually diminish.
History of glass. The history of glassmaking can be traced back to 3500 BCE in Mesopotamia, but Mesopotamians may have created second-rate copies of glass objects from Egypt, where this complex craft actually originated. Other archaeological evidence suggests that the first true glass was made in coastal north Syria, Mesopotamia or Egypt.
Later vessels were cut even more dramatically and by the 4th century CE, the art form reached its zenith with the highly carved diatreta or cage-cups and perhaps the most famous Roman glass vessel of all, the Lycurgus Cup.