When prehistoric man picked up his first stone he would not appreciate that its weight was due to the effect of gravity on its mass. Soon, though, he would learn that large objects were sometimes lighter than smaller ones and that he would need an aid to help compare weights and values. Today, we accept weighing as part of everyday life, using its principles as measures of our idea of justice, but giving methods of weighing little thought. Weighing, however, is an ancient art, which has exercised the minds of philosophers, scientists, engineers and even the dishonest for at least 6000 years. This book shows how men strove to produce a machine which would compare more accurately, or more quickly, or would meet a special need or perhaps sell even more cheaply. With the aid of many illustrations and non-technical language, some essential knowledge of the principles of weighing is provided.