De Verborum Significatu
Sextus Pompeius Festus
October equus appellatur, qui in campo Martio mense Octobri immolatur quotannis Marti, bigarum victricum dexterior. De cuius capite non levis contentio solebat esse inter Suburaneses, et Sacravienses, ut hi in regiae pariete, illi ad turrim Mamiliam id figerent; eiusdemque coda tanta celeritate perfertur in regiam, ut ex ea sanguis destillet in focum, participandae rei divinae gratia. Quem hostiae loco quidam Marti bellico deo sacrari dicunt, non ut vulgus putat, quia velut supplicium de eo sumatur, quod Romani Ilio sunt oriundi, et Troiani ita effigie in equi sint capti. Multis autem gentibus equum hostiarum numero haberi testimonio sunt Lacedaemoni, qui in monte Taygeto equum ventis immolant, ibidemque adolent, ut eorum flatu cinis eius per finis quam latissime differatur. Et Sallentini, aput quos Menzanae Iovi dicatus vivos conicitur in ignem. Et Rhodi, qui quotannis quadrigas soli consecratas in mare iaciunt, quod is tali curriculo fertur circumvehi mundum.
It is called the October Horse, which is sacrificed to Mars every year in the Campus Martius in the month of October, the right-hand horse of the victor's chariot. There used to be a serious contest over its head between the inhabitants of the Subura and those of the Via Sacra. The latter wanted to fix it to the wall of the regia, the latter to the tower of Mamilius. The tail of the horse was carried with all speed into the Regia, so that its blood could drip onto the hearth, and be used in sacred rites. Some people say that the horse is dedicated to the war god, Mars, in place of a victim, not as the common people think, because it was being punished, since the Romans originated in Troy and the Trojans were defeated by the likeness of a horse. The use of a horse as a sacrificial animal, moreover, is attested among many people. The Spartans sacrifice a horse to the winds atop Mt. Taygetes, and burn it there, so that by the blowing of the winds its ashes may be carried as widely as possible through their land. And the Sallentines, among whom a horse dedicated to Jupiter Menzana is driven alive into a fire. And the Rhodians, who every year throw into the sea quadrigas dedicated to the sun, because it is said to go around the world in such a chariot.
Translation by Jane W. Crawford, © 2001.