gems, gem testing, gemology, specific gravity, scales, weights, weighing

This unique survey of the history of weighting and its instruments, from the earliest known examples in the millennia before Christ to the modern era, is generously illustrated with 98 plates depicting scales, weights, and containers from the great collections of the world. It includes the known hallmarks of the scale and weight makers of Western Europe and lists of the weights of the world and their metric equivalents, by country and by name of weight. [RWH: Like most Western works, this book completely ignores the tremendous work done by Arabic-language scholars like al-Bīrūnī and al-Khazinī, who were measuring specific gravity hundreds of years before European scholars.]