According to Morel (Fam. Rom.) the worship of the Dioscuri, as         divinities, had it's origin at Rome, from the victory which the consul         Postumius gained, near the lake Regillus, over the Latins and the sons         of Tarquinius Superbus (B.C. 493 or 496). It was said that, after that         engagement, the Dioscuri appeared in the forum of Rome, wearing         conical bonnets, over each of which was a star. They stood resting upon         their lances, beside their horses, which were drinking at a fountain.         These twin heroes disappeared as soon as they had announced the news of         the battle, at a moment when, on account of the distance from the scene         of the slaughter, no one could have as yet become acquainted with the         event. It is also related that, during the action, two young men, mounted         on two white horses, were seen fighting valiantly for the Romans. This         legend is alluded toin the type of a consular denarius. See Postumia gens.

It also forms the subject of one of the most spirit-stirring poems in         Mr. Macaulay's "Lays of Ancient Rome", under the title of "the         Battle of the Lake Regillus, as sung at the feast of Castor and Pollux,         on the ides of Quintilis, in the year of the city CCCCLI." (B.C.         303). This characteristic tradition of supernatural powers crowning with         victory the arms of the yet young republic, is, by the author's genius         and his conversance with classic lore, filled to overflowing with warlike         incident, and with patriotic animation. After proclaiming to a great throng         of people,

  This day by lake Regillus,
            Under the Poreian height,
          All in the lands of Tusculum,
            Was fought a glorious fight,

the two strange horsemen, recognised by their pointed caps, and the stars         above them, as the "Great Twin Brethren, to whom the Dorians pray,"

  When they drew nigh to Vesta,
            They vaulted down amain,
          And wash'd their horses in a well,
            That springs by Vesta's fane.
          And straight again they mounted,
            And rode to Vesta's door,
          Then like a blast, away they past,
            And no man saw them more. (p.137)

image=http://www.forumancientcoins.com/Dictionary_Of_Roman_Coins/webimages/P331S0/M2_3.gif

On a denarius of the Sulpicia gens, struck in memory of L. Servivs Rvfvs         (son of Servius Sulpicius Rufus, a friend of Cicero's), the Dioscuri are         represented as two naked men, galeated, standing together, front faced,         armed with spears, which they hold transversely, as in the above engraving.         On another denarius, they stand holding their spears, with a horse on         each side of them, and a star over each of their heads. See Memmia gens.

The Dioscuri most frequently appear, on family coins, as horsemen galloping,         with couched lances, and stars above their pilei. See Atilia (p.         93); Horatia (p. 316); Cordia, conjoined heads of twin brothers (p. 280);         the same in Fonteia; Servilia (on horseback, proceding in opposite directions),         and many other consular denarii. In the imperial series, this type (which         was meant to denote brotherly concord), is of rare occurence. On a brass         medallion of Marcus Aurelius, and a second brass of Geta, one of the Dioscuri,         holding a spear, stands beside his horse. See Castor (p. 190). On a brass         medallion of Maxentius (valued by Mionnet at 100 fr.) they stand each         with the pileus on his head, and the pallium hanging behind         his back, holding his spear with one hand and his horse's bridle with         the other. There is a second brass of the same reign and type, the legend         being on both AETERNITAS AVG. N.
     

According to Morel (Fam. Rom.) the worship of the Dioscuri, as         divinities, had it's origin at Rome, from the victory which the consul         Postumius gained, near the lake Regillus, over the Latins and the sons         of Tarquinius Superbus (B.C. 493 or 496). It was said that, after that         engagement, the Dioscuri appeared in the forum of Rome, wearing         conical bonnets, over each of which was a star. They stood resting upon         their lances, beside their horses, which were drinking at a fountain.         These twin heroes disappeared as soon as they had announced the news of         the battle, at a moment when, on account of the distance from the scene         of the slaughter, no one could have as yet become acquainted with the         event. It is also related that, during the action, two young men, mounted         on two white horses, were seen fighting valiantly for the Romans. This         legend is alluded toin the type of a consular denarius. See Postumia gens.

It also forms the subject of one of the most spirit-stirring poems in         Mr. Macaulay's "Lays of Ancient Rome", under the title of "the         Battle of the Lake Regillus, as sung at the feast of Castor and Pollux,         on the ides of Quintilis, in the year of the city CCCCLI." (B.C.         303). This characteristic tradition of supernatural powers crowning with         victory the arms of the yet young republic, is, by the author's genius         and his conversance with classic lore, filled to overflowing with warlike         incident, and with patriotic animation. After proclaiming to a great throng         of people,

  This day by lake Regillus,
            Under the Poreian height,
          All in the lands of Tusculum,
            Was fought a glorious fight,

the two strange horsemen, recognised by their pointed caps, and the stars         above them, as the "Great Twin Brethren, to whom the Dorians pray,"

  When they drew nigh to Vesta,
            They vaulted down amain,
          And wash'd their horses in a well,
            That springs by Vesta's fane.
          And straight again they mounted,
            And rode to Vesta's door,
          Then like a blast, away they past,
            And no man saw them more. (p.137)

image=http://www.forumancientcoins.com/Dictionary_Of_Roman_Coins/webimages/P331S0/M2_3.gif

On a denarius of the Sulpicia gens, struck in memory of L. Servivs Rvfvs         (son of Servius Sulpicius Rufus, a friend of Cicero's), the Dioscuri are         represented as two naked men, galeated, standing together, front faced,         armed with spears, which they hold transversely, as in the above engraving.         On another denarius, they stand holding their spears, with a horse on         each side of them, and a star over each of their heads. See Memmia gens.

The Dioscuri most frequently appear, on family coins, as horsemen galloping,         with couched lances, and stars above their pilei. See Atilia (p.         93); Horatia (p. 316); Cordia, conjoined heads of twin brothers (p. 280);         the same in Fonteia; Servilia (on horseback, proceding in opposite directions),         and many other consular denarii. In the imperial series, this type (which         was meant to denote brotherly concord), is of rare occurence. On a brass         medallion of Marcus Aurelius, and a second brass of Geta, one of the Dioscuri,         holding a spear, stands beside his horse. See Castor (p. 190). On a brass         medallion of Maxentius (valued by Mionnet at 100 fr.) they stand each         with the pileus on his head, and the pallium hanging behind         his back, holding his spear with one hand and his horse's bridle with         the other. There is a second brass of the same reign and type, the legend         being on both AETERNITAS AVG. N.