Bi Disk, 206 BCE - 220 CE, 9 5/16 x 1/8 in. (23.65 x 0.32 cm) (outer diameter), Grey-green mottled nephrite (jade), China, 1st century CE, Originating in the Hongshan culture of the Neolithic period around 4000-3000 BCE, the bi disk, according to later Bronze Age interpretation, is emblematic of heaven. Although they retain the same decorative organization of the earliest examples, the bi disks from the Han dynasty tend to be more elaborate than their Neolithic predecessors. The outer band of this bi boasts openwork designs of pairs of dragons and phoenixes, whereas earlier examples display incised designs in solid stone. On the other hand, the raised bosses toward the center of this bi (known as guwen or 'grain pattern') are simpler in comparison to earlier Western Han examples, which were accompanied by incised spirals that suggested sprouting grainperhaps a symbol of fertility. By the late Han dynasty, the curving tail became less obvious or disappeared completely, as seen here.