In April 2012, LIVESCIENCE reported on the discovery of a 3rd century AD ship which sank near Trapani, Sicily. According to the report,
Her cargo, officially consisting of assorted jars once filled with walnuts, figs, olives, wine, oil and fish sauce, also contained many unusual tubular tiles. The unique tiles were apparently valuable enough for sailors to smuggle them from North Africa to Rome, where they sold for higher prices.
These tiles were used by Roman builders and were much cheaper in North Africa than in Rome. However, googling has not turned up any further examples of smuggling in the Roman Empire in the time period I'm interested in. Nor does the Cambridge Economic History of the Greco-Roman World appear to cover this.
As duties and the value of goods varied at different times, so (I would guess) did the amount of smuggling and the kinds of goods smuggled. presumably, items with low duties would not have been worth smuggling. Is there any evidence that (for example) salt and silk were smuggled? This source (from 1875) states,
the practice of smuggling appears to have been as common among the Romans as in modern times.
but gives no details.
What evidence is there for the smuggling of goods? Do we know what kinds of goods were most commonly smuggled?
As I’m not sure how broad this question is, answers could be restricted to the smuggling of goods into the Italian peninsula and Sicily, and / or to a shorter time period (in which case, preferably during the time of the Julio-Claudian dynasty).