Titus Livius (Livy), The History of Rome, Book 7
Rev. Canon Roberts, Ed.

3. However, the first introduction of plays, though intended as a means of religious expiation, did not relieve the mind from religious terrors nor the body from the inroads of disease. [2] Owing to an inundation of the Tiber, the Circus was flooded in the middle of the Games, and this produced an unspeakable dread; it seemed as though the gods had turned their faces from men and despised all that was done to propitiate their wrath. [3] ¹ C. Genucius and L. Aemilius Mamercus were the new consuls, each for the second time. The fruitless search for effective means of propitiation was affecting the minds of the people more than disease was affecting [4] their bodies. It is said to have been discovered that the older men remembered that a pestilence had once been assuaged by the Dictator driving in a nail. The senate believed this to be a religious obligation, and ordered a Dictator to be nominated for [5] that purpose. L. Manlius Imperiosus was nominated, and he appointed L. Pinarius as his Master of the Horse.

There is an ancient instruction written in archaic letters which runs: Let him who is the praetor maximus fasten a nail on the Ides of September. This notice was fastened up on the right side of the temple of Jupiter Optimus Maximus, next to the chapel [6] of Minerva. This nail is said to have marked the number of the year —written records being scarce in those days —and was for that reason placed under the protection of Minerva because she was the inventor [7] of numbers. Cincius, a careful student of monuments of this kind, asserts that at Volsinii also nails were fastened in the temple of Nortia, an Etruscan goddess, to indicate the number of [8] the year.

It was in accordance with this direction that the consul Horatius dedicated the temple of Jupiter Optimus Maximus in the year following the expulsion of the kings²; from the consuls the ceremony of fastening the nails passed to the Dictators, because they possessed greater authority. As the custom had been subsequently dropped, it was felt to be of sufficient importance to require the appointment of a Dictator.

[9] L. Manlius was accordingly nominated, but, regarding his appointment as due to political rather than to religious reasons and eager to command in the war with the Hernici, he caused a very angry feeling among the men liable to serve by the inconsiderate way in which he conducted the enrolment. At last, in consequence of the unanimous resistance offered by the tribunes of the plebs, he gave way, either voluntarily or through compulsion, and laid down his Dictatorship.