<P> In Western countries, it is customarily worn on the left hand ring finger, though customs vary across the world . </P> <P> Before agreeing to marry, a couple may choose to buy and wear pre-engagement rings, also called promise rings . After marrying, the couple may wear both engagement rings and wedding rings, or if they prefer, only the wedding rings . Some brides have their engagement and wedding rings permanently soldered together after marriage . </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 diamonds become popular for engagement rings