Pliny: Natural History, Vol. IX (Loeb)

28 Its use must have begun to be more celebrated with the introduction of usury. A proof of this is the custom of the common people, with the ring still jumping out during bets, derived from the time when there was not yet a faster method of pledge, so that we can clearly affirm that money began among us first, and rings afterward. About money we shall speak a little later.

29 VII. Rings distinguished the other order from the plebs once they began to be celebrated, just as the tunic distinguished the senate from the rings. Although this, too, happened late, and we find that tunics with a wider purple stripe were commonly used even by heralds, just as the father of L. Aelius Stilo Praeconinus, so nicknamed for that reason. But rings clearly inserted a third, middle order between the plebs and the fathers, and what the military horses had previously given as a name, this the indices of wealth now assign. Nor was this done long ago.

30 When the divine Augustus was organizing the panels, the majority of the judges were in the iron ring class, and these were not called Knights, but Judges. The name of the Knights remained in the squadrons of public horses. Also, there were at first only four panels of judges, and scarcely a thousand were found in the panels, as the provinces had not yet

been added to this.