For measuring corn a bronze vessel, shaped rather like a bucket and called a modius, was used. The modius was a Roman dry measure used primarily to measure out flour and grain. It was one - third of an amphora (a tall jar in which wine, oil, and other products were carried in the holds of ships). The modius symbolizes an abundant grain supply. One often encounters the word "corn" when reading about the roman world. When corn is mentioned in modern times , people mean the maize plant or its product. Maize is a grain that is indigenous to America (which wasn't discovered yet in roman times ). When the ancients referred to corn, they meant "grain", usually wheat or barley. They would say "ears of corn" where we would say "heads of grain."