The bi (璧) is a type of circular ancient Chinese jade artifact. It is a flat jade disc with a circular hole in the centre. The earliest bi were produced in the Neolithic period, particularly by the Liangzhu culture (3400–2250 BCE). Later examples date mainly from the Shang, Zhou and Han dynasties. Neolithic bi are undecorated, while those of later periods of China, like the Zhou dynasty, bear increasingly ornate surface carving (particularly in a hexagonal pattern) whose motifs represented deities associated with the sky (four directions) as well as standing for qualities and powers the wearer wanted to invoke or embody. As laboriously crafted objects, they testify to the concentration of power and resources in the hands of a small elite. The jade, like bi disks, has been used throughout Chinese history to indicate an individual of moral quality, and has also served as an important symbol of rank. They were used in worship and ceremony – as ceremonial items they symbolised the ranks of emperor and kings.