The Roman historian Livy (about 59 BC - AD 17) mentions that before the invention of silver coinage, when money consisted of 'heavy bronze', wealthy Romans of the fourth century BC transported their money from one place to another in wagons. The 'heavy bronze' took the form of cast ingots weighing about 1600 grams (around 5 Roman pounds). They had a variety of designs on either side. They seem to have been used as a means of making official payments, such as taxes or judicial fines. Their value was used as a unit to assess a citizen's wealth.The ingots were no longer made after the mid-third century BC, when the Romans moved over entirely to silver coins. But bronze remained important within the Roman monetary system. The Latin word for bronze, aes, was the colloquial word for money.The elephant design on this example was probably inspired by the war-elephants in the army of the Greek king Pyrrhus who invaded Italy and attacked the Romans in 280 BC. This was the first time the Roman army had ever faced elephants in battle. Pyrrhus defeated the Romans twice, but he lost so many of his own men in the process that he eventually lost the war, hence the phrase a 'Pyrrhic victory'. The pig on the other side may refer to a bizarre occasion when, in one of the battles, Pyrrhus' elephants were frightened away by the grunting of pigs kept by the Roman army.