<P> In Anglo - Saxon countries, it is customarily worn on the left hand ring finger, but customs vary considerably elsewhere across the world . </P> <P> A couple in a committed relationship may give each other and wear pre-engagement rings, also called friendship or promise rings . Neither the engagement nor any other ring is worn during the wedding ceremony, when the wedding ring is put by the groom on the finger of the bride as part of the ceremony, and sometimes by the bride onto the groom's finger . After the wedding, the engagement ring is usually put back on, and is usually worn on the outside of the wedding ring . Some brides have their engagement and wedding rings permanently soldered together after the wedding . </P> <P> Although the ancient Egyptians are sometimes credited with having invented the engagement ring, and the ancient Greeks with having adopted the tradition, the history of the engagement ring can only be reliably traced as far back as ancient Rome . </P> <P> In many countries, engagement rings are placed on the ring finger of the left hand . At one time it was believed that this finger contained a vein (the vena amoris) that led to the heart . This idea was popularized by Henry Swinburne in A treatise of Spousals, or Matrimonial Contracts (1686). The story seems to have its origin in the ancient Roman book Attic Nights by Aulus Gellius quoting Apion's Aegyptiacorum, where the alleged vein was originally a nervus (a word that can be translated either as "nerve" or "sinew"). </P>

When did the tradition of diamond engagement rings start