Chinese Southern Song Dynasty Guanware Cong-form Vase
The shape of the Cong vase originates in the jade civilization of Qijia Culture in ancient China. It is characterized by square section and a circular mouth, which is consistent with Yin-Yang theory in ancient China---The sky is round and the earth is square.
"sky round earth square" concept is an embodiment of Yin-Yang theory, which is the essence of Chinese extensive and profound traditional culture. The theory, with an idea of Naive Dialectic, is a mode of thinking for Chinese sages to recognize the world, and thousands of years of social practices have proved its correctness.
The ancient Chinese refer to the condition when Heaven and Earth have not been separated from chaos as Taiji. Then Taiji gives birth to two forms, named Yin and Yang, and heaven and earth are separated. The ancient Chinese refer to the vast universe composed of many stars as Heaven while the land they live on and by as Earth. Since the stars like the Sun and the Moon are perpetually moving in cycles just like a closed circle without beginning and end, while the earth is silently carrying us just as a square still and steady object, and thus "sky round earth square" concept comes into being.
The center circular hole is regarded by ancient people as the way to Heaven for the soul after death. However, this Guanware Cong is used for flower arrangement by its owner, which is enough to surprise and puzzle ancient Chinese.