The Urine Tax (vectigal urinae)

In ancient Rome, urine was a valuable, heavily-regulated commodity used for industrial and commercial purposes. Romans didn't use modern soap; instead, laundromats called Fullonicae used stale urine because urea breaks down into ammonia, which cuts through grease, stains, and dirt in wool and togas. Workers (fullers) stomped on the clothes in vats of urine in a process known as the saltus fullonicus before rinsing them. Public urinals were placed across Rome, and pots or jars sat on street corners for citizens to contribute. Fullers and launderers bought the collected urine in bulk. Nero was the first to tax the urine trade (vectigal urinae), which was revived by Emperor Vespasian around 70 AD.

When Vespasian's son Titus complained about the gross nature of taxing urine, Vespasian held up a gold coin and asked if it smelled.

When Titus said no, the emperor replied, "Atqui ex lotio est" ("Yet it comes from urine"). This birthed the famous Latin phrase pecunia non olet. ("money does not stink") The phrase pecunia non olet is still used today to say that the value of money is not tainted by its origins. Vespasian's name still attaches to public urinals in Italy (vespasiano) and France (vespasienne).

Fresco of the so-called Pilastro dei Fullones from the fullonica of Veranius Hypsaeus in Pompeii (House VI 8, 20-21.2), depicting fullers.