Exodus 39:7-9

Young's Literal Translation

⁷ and he setteth them on the shoulders of the ephod -- stones of memorial for the sons of Israel, as Jehovah hath commanded Moses.

⁸ And he maketh the breastplate, work of a designer, like the work of the ephod, of gold, blue, and purple, and scarlet, and twined linen;

⁹ it hath been square; double they have made the breastplate, a span its length, and a span its breadth, doubled.