Let's keep learning about the ancient Chinese Six Ritual Jade sculptures
We already learned about the Bi disc - for the heaven or sky.
The second one is Cong, which is for the earth.
The cong is usually a tube with a circle shaped inside and a square shaped outside.
(from: wikipedia - cong (vessel))
Kid Facts - Blast from the past: Pietà - Michelangelo Buonarroti