Many different standards have been used in India for various purposes, one for the weighing of gold, another for the weighing of silver, another used by jewellers, and yet another by the medical tribe, but all alike start from the ratti.
“The determination of the true weight of the ratti has done much both to facilitate and give authority to the comparison of the ultimately divergent standards of the ethnic kingdoms of India. Having discovered the guiding unit, all other calculations become simple, and present singularly convincing results, notwithstanding that the bases of all these estimates rest upon so erratic a test as the growth of the seed of the gunjá-creeper (Abrius precatorius) under the varied influences of soil and climate. Nevertheless the small compact grain, checked in early times by other products of nature, is seen to have the remarkable faculty of securing a uniform average throughout the entire continent of India, which only came to be disturbed when monarchs like Shîr Shâh and Akbar in their vanity raised the weight of the coinage without any reference to the numbers of rattis, inherited from Hindu sources, and officially recognized in the old, but entirely disregarded and left undefined in the reformed Muhammadan mintages7.” We shall learn shortly that in its uniformity the ratti does not differ from other seeds such as wheat and barley. Probably, however, the fact that the gunjá-creeper was found everywhere in India gave it its position of a universal standard. Those who wish to study the elaborate systems of later times employed in India can consult the works of Colebrooke and Thomas already referred to.
The legislators Manu, Yájnavalkya, and Nárada trace all weights from the least visible quantity which they concur in naming trasareṇu and describing as the very small mote, “which may be discovered in a sunbeam passing through a lattice.” Writers on medicine proceed a step further, and affirm that a trasareṇu contains 30 paramáṇu or atoms. The legislators above-named proceed from the trasareṇu as follows: