The widespread use of posca is attested by numerous mentions by ancient sources ranging from the natural histories of Pliny the Elder to the comedies of Plautus. When on campaign, generals and emperors could show their solidarity with common soldiers by drinking posca, as did Cato the Elder (as recorded by Plutarch) and the emperor Hadrian, who according to the Historia Augusta "actually led a soldier’s life…and, after the example of Scipio Aemilianus, Metellus, and his own adoptive father Trajan, cheerfully ate out of doors such camp-fare as bacon, cheese and vinegar." A decree of AD 360 ordered that lower ranks of the army should drink posca and wine on alternate days.
Girolamo Cardano, in his Encomium Neronis of 1562, attributed the superiority of the Roman armies to only three factors: the great quantities of levies, their sturdiness and ability to carry heavy weights due to training, and good foods such as salted pork, cheese, and the use of posca as a drink.
The word posca is derived from either the Latin potor ("to drink") or from the Greek epoxos ("very sharp"). As the Greeks lacked a word for posca, sources written in Greek, such as Plutarch and the Gospels, use the word οξος (oxos, "vinegar") in its place (translated as acetum in the Vulgate Bible). The word eventually migrated into Greek from about the 6th century AD onwards as the Byzantine army continued the Roman tradition of drinking what they termed phouska.
Posca was composed of watered-down wine vinegar, but at times it could have included other herbs to improve the taste. For example, the Byzantine writers Aëtius of Amida and Paul of Aegina, from the 6th and 7th centuries, recorded a posca recipe used for laxative purposes that included cumin, fennel seed, celery seed, anise, thyme, and salt.
- Dalby, Andrew. "Posca" entry in Food in the Ancient World from A to Z, p. 270. Routledge, 2003. ISBN 0-415-23259-7
- Cardano, Girolamo. Emperor Nero: Son of Promise, Child of Hope (translated by Angelo Paratico) pp.185-6, Gingko Edizioni, Verona, 2019. ISBN 978-1689118538
- Roth, Jonathan. The Logistics of the Roman Army at War (264 B.C.-A.D. 235), pp. 37-38. BRILL, 1999. ISBN 90-04-11271-5
- Dalby, Andrew. Tastes of Byzantium: The Cuisine of a Legendary Empire, page 90. I.B. Tauris, 2010.
- Pliny the Elder [-79 CE], trans. John Bostock and Henry Thomas Riley, "Wines Drunk by the Ancient Romans", The Natural History [c. 77 CE], book 14, ch. 15. London: H.G. Bohn, 1855. 253, available online at books.google.com/books?id=A0EMAAAAIAAJ&pg=PA253