The form of these vases is based on a jade cong ritual object with a circular core and a square exterior, often with stylized masks carved in horizontal registers at the corners. For an example, see the jade cong dating to the Neolithic Period, Liangzhu Culture, in the Nanjing Museum, included in the Solomon R. Guggenheim Museum Exhibition, China, 5000 Years, New York, 1998, no. 5.
Ceramic vases of archaistic cong form were produced as early as the Song dynasty at the Guan and Longquan kilns, such as a Guan vase with notches on four corners from the Percival David Foundation and now housed at the British Museum, illustrated by Rosemary Scott in Percival David Foundation of Chinese Art. A Guide to the Collection, London, 1989, fig. 42.