Gaius Plinius Secundus, a Roman, was better known as Pliny the Elder:
Pliny the Elder (23/4-79 CE): Natural History, XXXIII.6: Luxury in the Use of Rings: It was the custom at first to wear rings on a single finger only---the one next to the little finger, and this we see to be the case in the statues of Numa and Servius Tullius. Later it became usual to put rings on the finger next to the thumb, even with statues of the gods; and more recently still it has been the fashion to wear them upon the little finger too. Among the Gauls and Britons the middle finger---it is said---is used for the purpose. At the present day, however, with us, this is the only finger that is excepted, for all the others are loaded with rings, smaller rings even being separately adapted for the smaller joints of the fingers.
Some people thrust several rings upon the little finger alone; while others wear but one ring upon this finger, the ring that carries the seal upon the signet ring itself, this last being carefully shut up as an object of rarity, too precious to be worn in common use, and only to be taken from the coffer as from a sanctuary. And thus is the wearing of a single ring upon the little finger, no more than an ostentatious advertisement that the owner has property of a more precious nature under seal at home.
Some too make a parade of their rings, whilst to others it is a decided labor to wear more than one at a time; some, in their solicitude for the safety of their gems, make the hoop of gold tinsel, and fill it with lighter material than gold, thinking thereby to diminish the risks of a fall. Others again, are in the habit of concealing poisons beneath their ring stones, and so wear them as instruments of death; so e.g. did Demosthenes, mightiest of Greek orators. And besides, how many of the crimes that are stimulated by cupidity, are committed by the instrumentality of rings!
Happy the times; yes, truly innocent when no seal was ever put on anything! At the present day, indeed, our very food and drink even have to be kept from theft through the agency of the ring. This of course is thanks to those legions of slaves, those throngs of foreigners who are introduced into our houses, multitudes so great that we have to have a nomenclator [professional remembrancer] to tell us even the names of our own servants. Different surely it was in the times of our forefathers, when each person possessed a single slave only, one of his master's own lineage, called Marcipor [Marcus's boy] or Lucipor [Lucius's boy], from his master's name, as the case might be, and taking all his meals with him in common; when, too, there was no need to take precautions at home by keeping a watch upon the servants. But at present, we not only buy dainties that are sure to be pilfered but hands to pilfer them as well; and so far from its being enough to keep the very keys sealed, often the signet ring is taken from the owner's finger while he is overpowered with sleep, or actually lying on his death bed.
[Source: William Stearns Davis, ed., Readings in Ancient History: Illustrative Extracts from the Sources, 2 Vols. (Boston: Allyn and Bacon, 1912-13), Vol. II: Rome and the West.]