Ab urbe condita

For it was a settled rule amongst the augurs that their number was bound to consist of threes, so that the three ancient tribes of the Ramnes, Titienses, and Luceres might each have their own augur, or if more were needed, the same number should be added for each. This was the principle on which they proceeded when by adding five to four the number was made up to nine, so that three were assigned to each tribe.