Zosimus, New History 2.03
Zosimus (Greek Ζώσιμος): Early Byzantine, pagan author of a history of the Roman Empire, published in the first quarter of the sixth century CE.
The translation of Zosimus' New History offered here was printed in 1814 by W. Green and T. Chaplin in London, and was probably prepared by J. Davis of the Military Chronicle and Military Classics Office. The translator is anonymous. The text was found at Tertullian.org. The notes were added by Jona Lendering.
[2.3.1] This same altar, and the manner of sacrificing on it, thus originated. The Romans and the Albans being at war, and both prepared for battle, a monstrous figure appeared, clothed in a black skin, and crying out that Pluto and Proserpine commanded sacrifices to be made to them before they fought, it disappeared.
[2.3.2] On which the Romans, who were terrified at the sight, made an altar underground, and when they had sacrificed on it, buried it at the depth of twenty feet in order that it might not be found by any but themselves. Valesius having found it, according to command, sacrificed upon it, and kept the vigils; for which he was called Manius Valerius Tarentinus. For the Romans call the infernal gods Manes, and valere signifies to be in good health; and the surname of Tarentinus he derived from Tarentum where he sacrificed.
[2.3.3] Some time afterwards, when a plague happened in the city, which was the year after the expulsion of the kings, Publius Valerius Publicola sacrificed a black bull and a black heifer to Pluto and Proserpine, by which he freed the city from the disease. He wrote on the altar this inscription:
Publius Valerius Publicola dedicated fire to Pluto and Proserpine in the Campus Martius, and exhibited spectacles in honor of them, for the preservation of the Roman people.note[A better translation is "Some time afterwards, when a plague occurred in the city in the first year after the kings, Publius Valerius Publicola having sacrificed to Pluto and Persephone on this altar a black bull and a black heifer, he delivered the city from the disease. He inscribed these words on the altar: 'Publius Valerius Publicola consecrated the fire-bearing plain to Pluto and Persephone, and held spectacles in honor of Pluto and Persephone, for the deliverance of the Roman people'." (Thanks to William P. Thayer of LacusCurtius.]