 The "bi" is a circular disk with a hole, originally usually plain, but increasingly decorated, and the "cong" is a vessel, square on the outside but circular inside.In later literature the "cong" represents the earth and the "bi" the sky.Jades of the Shang, Zhou, and Han dynasties are increasingly embellished with animal and other decorative motifs characteristic of those times, and craftsmen developed great skill in detailed low relief work in objects such as the belt-hooks that became part of elite costume.