Excerpts from Chinese Astronomical Jades
an article written by Henri Michel for Popular Astronomy VOL LVIII No. 5 May 1950

"Chinese jade objects are the oldest astronomical instruments which have reached us. They were used during the tenth century, B.C. and perhaps earlier. These jades have been known by collectors under the designation of "astronomical jades," although nobody explains why they were so called. There is a vague tradition that they might have been used in ritual ceremonies, for the worship of heaven and earth, but even Chinese commentators seem unable to tell their real purpose. Some ancient texts also mention an enigmatic object, called siun-ki yu-heng, explaining in very sibylline terms that this was an instrument for "observing the constellations" and "knowing the celestial houses". A Chinese mathematician of the 2nd century, Tcheng-Hiuan, writes as follows:

"The part of the instrument that had a turning motion was the ki; the part which was held in the hand for observing was the heng; both were made of jade. With them were measured the degrees of motions." The words siun-ki and yu-heng have a clear meaning; ki is a rotating instrument; siun is a special quality jade; heng is a tube, made of ordinary jade: yu. The siun-ki yu-heng consists thus of two parts: the instrument itself, and the tube."

"Collectors know another jade disk, the pi (or bi) which is a simple round plate with a central hole. According to an old Chinese ritual book, the pi was a symbol of heaven, while the tube ts,ung was the symbol of the earth. Nobody tells how or why. I think that pi and ts'ung are evolved from the ki and the heng and that initially the first was used for the observation of the stars, while the second was adjusted to the terrestrial horizon. In this way, these jades were related to heaven and earth. Of course the learned did not divulge this to profanes, and veiled it under mysterious ceremonies. With time, during the terrible wars of the last centuries, B.C., and the systematic destruction of books in 213, the scientific meaning of the instrument was lost, and only a vague esoteric tradition remained."