Titus Livius (Livy), The History of Rome, Book 1
Benjamin Oliver Foster, Ph.D., Ed.

43. Out of those who had a rating of a hundred thousand assess¹ or more he made eighty [p. 151]centuries, forty each of seniors and of juniors; these² were all known as the first class; the seniors were to be ready to guard the city, the juniors to wage war abroad. [2] The armour which these men were required to provide consisted of helmet, round shield, greaves, and breast-plate, all of bronze, for the protection of their bodies; their offensive weapons were a spear and a sword. [3] There were added to this class two centuries of mechanics, who were to serve without arms; to them was entrusted the duty of fashioning siege-engines in war. [4] The second class was drawn up out of those whose rating was between a hundred thousand and seventy-five thousand; of these, seniors and juniors, twenty centuries were enrolled. The arms prescribed for them were an oblong shield in place of the round one, and everything else, save for the breast-plate, as in the class above. [5] He fixed the rating of the third class at fifty thousand; a like number of centuries was formed in this class as in the second, and with the same distinction of ages; neither was any change made in their arms, except that the greaves were omitted. [6] In the fourth class the rating was twenty-five thousand; the same number of centuries was formed, but their equipment was changed, nothing being given them but a spear and a javelin. [7] The fifth class was made larger, and thirty centuries were formed. These men carried slings, with stones for missiles. Rated with them were the horn-blowers and trumpeters, divided into two centuries. Eleven thousand was the rating of this class. [8] Those who were assessed at less than this amount, being all the rest of the population, were made into a single century, exempt from military service. When the [p. 153]equipment and distribution of the infantry had been³ thus provided for, Servius enrolled twelve centuries of knights out of the leading men of the state. [9] He likewise formed six other centuries —three had been instituted by Romulus —employing the same names which had been hallowed to their use by augury. For the purchase of horses they were allowed ten thousand asses each from the state treasury, and for the maintenance of these horses unmarried women were designated, who had to pay two thousand asses each, every year. All these burdens were shifted from the shoulders of the poor to those of the rich. [10] The latter were then granted special privileges: for manhood suffrage, implying equality of power and of rights, was no longer given promiscuously to all, as had been the practice handed down by Romulus and observed by all the other kings; but gradations were introduced, so that ostensibly no one should be excluded from the suffrage, and yet the power should rest with the leading citizens. [11] For the knights were called upon to vote first; then the eighty centuries of the first class: if there were any disagreement there, which rarely happened, it was provided that the centuries of the second class should be called; and they almost never descended so far as to reach the lowest citizens. [12] Nor ought it to cause any surprise that the present organization, which exists since the increase of the tribes to thirty-five, and the doubling of their number in the matter of the junior and senior centuries, does not correspond with the total established by Servius Tullius. [13] For, having divided the City according to its inhabited regions and hills into four parts, he named them “tribes,” a word [p. 155]derived, I suppose, from “tribute”;⁴ for this⁵ likewise the same king planned to have apportioned equitably, on the basis of the census; nor had these tribes anything whatever to do with the distribution or the number of the centuries.