Pi Disk

Pi Disk
Ch'i-chia Culture (ca. 2200-1800 B.C.)
Max. diameter: 28.4 cm, diameter of hole: 5.35 cm, thickness: 1.9 cm

??Carved from light green jade, the surface of this disk has weathered to a reddish hue. Uneven in thickness, one side protrudes slightly yet is still level. The other side is damaged. The hole was drilled from one side and is relatively small in diameter.

??The level side is engraved on the left and right with poetry of the Ch?ien-lung Emperor (r. 1736-1795), whose imperial seals appear engraved at the top and bottom. Only an imperial seal is engraved on the back at the top and bottom. A square sandalwood screen stand with a plug in the middle was specially designed for the disk.

 

Traditional studies on pi disks in "Illustrated Study of Ancient Jades"
...mention that the round shape of the pi disk was a symbol for the heavens and that green pi disks were used to venerate heaven.