璧 is one of the 'Six Auspicious Jades' (
六瑞 liù ruì) used in Zhou dynasty ritual to communicate with heaven, while the related
玉琮 (cong, a tube) communicated with earth. Excavations of
璧 from elite Neolithic and Bronze Age tombs (Liangzhu, Hongshan) show its ritual importance long predates writing.