Note:  Do not rely on this information. It is very old.

Urim and Thummim

Urim and Thummim (Light and Perfection or Doctrine and Truth) was the Hebrew name which denoted an instrument of divination which was in use among the ancient Hebrews, and which was in some way connected with the breastplate worn by the High Priest. Commentators on the Bible, which makes more than one mention of Urim and Thummim, are in doubt whether the name applied to the whole breastplate or only to certain jewels upon it. Jewish writers consider that the oracle made itself known by exceptional brightness in the jewels.