Was there a single ruler that standardized Roman measurements, like Qinshihuangdi for China? I remember in history class we talked about how the Romans had standard weight units in markets and axle widths for roads. Were these imposed by the government? Or did a common measurement just end up slowly pervading the entire empire? (e.g. some popular chariot-maker used axles 1.4m wide, which created 1.4m wide ruts, which led more people to build 1.4m wide chariots, which created deeper 1.4m wide ruts, cycling ad infinitum)
I found the following in the
Oxford Encyclopedia of Ancient Greece and Rome. (I accessed this through my university so I can't provide a link unfortunately)
Roman weights and measures can be determined from existing archaeological artifacts including coins, from dipinti (painted inscriptions) on containers, and from inventory lists. One of the main surviving treatises on ancient weights and measures was written by Epiphanius, bishop of Salamis on Cyprus, at the end of the fourth century ce.
An analysis of Roman weights recovered from Pompeii and Herculaneum suggests that the average weight of a Roman pound was around 323 grams (the modern pound is 453.6 grams), though a Roman pound is often expressed in modern scholarship (and previously defined by August Böckh in 1838) as 327.45 grams. An official libra (pound) bronze weight from Alchester in Oxfordshire, England, weighs only 320.35 grams. A set of four rectangular lead weights were discovered at Charterhouse-on-Mendip in Somerset (Roman Inscriptions of Britain, vol. 2, fascicle 2, 2412.5–8). Each is marked with the symbol for 1, 2, 3, or 4 unciae (ounces), though each is slightly light. Another set, which ranges from 1 uncia to 41 librae, comes from the fort at Templeborough in Yorkshire (Roman Inscriptions of Britain, vol. 2, fascicle 2, 2412.37–47). Coin weights suggest a slightly different unit, but these discrepancies may be the result of other factors, perhaps chronological.
My reading of this is that if there were standardized weights and measures they may have varied over time and place. Second, it appears that the current archaeological record is far from complete and as a result it's hard to say when/who standardized the weights and measures. I could be wrong but I haven't been able to find any sources that indicate a fixed time/person who standardized the weights and measures.
Additionally, this paper on Vitruvious might be of interest, as it appears that Vitruvious' book De Architectura is one of the Roman texts densest in measurements.