Lucae Paeti ... de mensuris, et ponderibus Romanis, et Graecis

less than twenty thousand remain, they occupy the whole day; clearly, if there are twenty-one thousand paces, two days are attributed to him." Since miles began to be marked on roads with stone columns, it is read everywhere that they were called "stones" by writers. This, however, I think was invented by C. Gracchus; for I do not remember having read that it was done before. Concerning which, Plutarch in his life. "To these," he says, "he measured the whole road by miles (a mile contains a little less than eight stadia) and placed stone columns, for the sake of marking the space." This he said. In which place it should be noted, which I also said a little before, that Plutarch, in what he said, that eight stadia are a little less than a mile, did not observe the difference of the Roman and Greek foot. That miles were called "stones" is clearer than that it needs proof; I will, however, be content with three places from Pliny. Book 15, chapter 18, concerning the Carthaginian fig brought into the Senate by Cato: "The Carthaginian camp was not entrenched at the third stone." And Book 31, chapter 3, concerning the Aqua Virgo channeled by Agrippa: "He brought the Virgo from the turn-off of the eighth stone." And Book 36, chapter 15, concerning the channel of the Aqua Claudia: "Indeed, from the fortieth stone, the Curtius and Caeruleus springs flowed with such height that they could be lifted onto all the hills of the city." To these may be added that of Martial, book 10 of epigrams, concerning Torquatus and Otacilius:

Torquatus has his estate at the fourth stone:
At the fourth, Otacilius digs out his small plot.

Some vestiges of which stones, or columns, still occur on the Appian Way for those going from Rome to Naples; for they are stone columns: of which one also is at the gate of the city of Fundi, at the entrance, if I remember correctly, on the left, on which the number of miles, by which the columns themselves are distant from the city, is seen marked.
The actus minimus smallest unit of land has in width four feet, in length 120 feet. Columella (Book 5, chapter 1): "The actus minimus, as Varro says, has 120 feet of length, 4 feet of width."
A clima, by the same witness Columella where above, is 60 feet in every direction.
The actus quadratus square actus is bounded on all sides by 120 feet, with the witness Columella in the place just mentioned, and Varro on rustic affairs (Book 1, chapter 10).
The iugerum acre is so called from the fact that it contains two actus quadrati joined together...