beds of rivers, was cast into bars, or in the shape of dust made part of the regular tribute of the southern provinces of the empire. The traffic was carried on partly by barter, and partly by means of a regulated currency of different values. This consisted of transparent quills of gold dust, bits of tin cut in the form of T, and bags full of cacao containing a specified number of grains[1].
From this we get an insight into the first beginnings of weights. Some natural unit (and by natural I mean some product of nature of which all specimens are of uniform dimension) is taken, such as the quill used by the Aztecs. The average-sized quill of any particular kind of bird presents a natural receptacle of very uniform capacity. These quills of gold-dust were estimated at so many bags containing a certain number of grains. The step is not a long one to the day when some one will balance in a simple fashion quills of gold dust against seeds of cacao, and find how much gold is equal to a nut. Nature herself supplies in the seeds of plants weight-units of marvellous uniformity. If any one objects to my assumption that the Aztecs were on the very verge of the invention of a weight system, my answer is that another race of America, whose political existence ceased under the same cruel conditions as that of their Northern contemporaries, I mean the Incas of Peru, who were in a stage of civilization almost the same as that of the Aztecs, had already found out the art of weighing before the coming of the Spaniards, although they were inferior to the Mexicans in so far as they had not a well-defined system of hieroglyphic writing, nor of currency such as the latter possessed. Scales made of silver have been discovered in Inca graves[2]. The metal of which they are made shows that they were only employed for weighing precious commodities of small bulk.
Unfortunately I can find no record of weights having been found along with the silver scales in the Inca graves. If the weights were simply natural seeds, they would easily perish, or even if perfect when the tombs were opened, would be simply
