even before 250 BC into numbered miles, and most viae after 124 BC. The modern word "mile" derives from the Latin milia passuum, "one thousand paces", each of which was five Roman feet, or in total . A milestone, or miliarium, was a circular column on a solid rectangular base, set for more than into the ground, standing tall, in diameter, and weighing more than 2 tons. At the base was inscribed the number of the mile relative to the road it was on. In a panel at eye-height was the distance to the Roman Forum and various other information about the officials who made or repaired the road and when. These miliaria are valuable historical documents now. Their inscriptions are collected in the volume XVII of the Corpus Inscriptionum Latinarum. The Romans had a preference for standardization wherever possible, so Augustus, after becoming permanent commissioner of roads in 20 BC, set up the miliarium aureum ("golden milestone") near the Temple of Saturn. All roads were considered to begin from this gilded bronze monument. On it were listed all the major cities in the empire and distances to them. Constantine called it the umbilicus Romae ("navel of Rome"), and built a similar—although more complex—monument in Constantinople, the Milion. Milestones permitted distances and locations to be known and recorded exactly. It was not long before historians began to refer to the milestone at which an event occurred. Itinerary maps and charts Combined topographical and road-maps may have existed as specialty items in some Roman libraries, but they were expensive, hard to copy and not in general use. Travelers wishing to plan a journey could consult an itinerarium, which in its most basic form was a simple list of cities and towns along a given road, and the distances between them. It was only a short step from lists to a master list, or a schematic route-planner in which roads and their branches were represented more or less in parallel, as in the Tabula Peutingeriana. From this master list, parts could be copied and sold on the streets. The most thorough used different symbols for cities, way stations, water courses, and so on. The Roman government from time to time would produce a master road-itinerary. The first known were commissioned in 44 BC by Julius Caesar and Mark Antony. Three Greek geographers, Zenodoxus, Theodotus and Polyclitus, were hired to survey the system