In divine things, the same order he preserved throughout, as far as concerns those things which are performed to the gods. For sacred things are performed by men in places and times. These four things I have mentioned he embraced in twelve books, allotting three to each. For he wrote the first three concerning men, the following three concerning places, the third three concerning times, and the fourth three concerning sacred rites, -- showing who should perform, where they should perform, when they should perform, what they should perform, with most subtle distinction. But because it was necessary to say -- and that especially was expected -- to whom they should perform sacred rites, he wrote concerning the gods themselves the last three books; and these five times three made fifteen. But they are in all, as we have said, sixteen. For he put also at the beginning of these one distinct book, speaking by way of introduction of all which follows; which being finished, he proceeded to subdivide the first three in that five-fold distribution which pertain to men, making the first concerning high priests, the second concerning augurs, the third concerning the fifteen men presiding over the sacred ceremonies.  The second three he made concerning places, speaking in one of them concerning their chapels, in the second concerning their temples, and in the third concerning religious places. The next three which follow these, and pertain to times, -- that is, to festival days, -- he distributed so as to make one concerning holidays, the other concerning the circus games, and the third concerning scenic plays. Of the fourth three, pertaining to sacred things, he devoted one to consecrations, another to private, the last to public, sacred rites. In the three which remain, the gods themselves follow this pompous train, as it were, for whom all this culture has been expended. In the first book are the certain gods, in the second the uncertain, in the third, and last of all, the chief and select gods.
 Tarquin the Proud, having bought the books of the sibyl, appointed two men to preserve and interpret them (Dionys. Halic. Antiq. iv. 62. These were afterwards increased to ten, while the plebeians were contended for larger privileges; and subsequently five more were added.