⚠The woodcut print shows some wear and ink bleeding, making some smaller characters in the lower text block and within the diagram difficult to decipher clearly.

Map of the Armillary Sphere and Celestial Engine

[The central illustration consists of a circular celestial chart. At the top, the constellation of the Big Dipper original: 北斗 (Beidou) is depicted with linked stars. The circular diagram itself contains multiple rings: an inner ring with symbols and names of the Five Elements Wood, Fire, Earth, Metal, and Water and central celestial regions like the Supreme Palace original: 太微 (Taiwei) and the Purple Forbidden Enclosure original: 紫微 (Ziwei), the area around the North Star; and an outer ring listing the Twenty-Eight Mansions Lunar stations, such as the Horn, Neck, Root, Room, Heart, Tail, and Winnowing Basket. Labels for cardinal directions like True North are placed outside the perimeter.]

True North

The description attached to the instrument states that the "Engine and Transverse" original: Xuanji Yuheng (璿璣玉衡) refer to the Big Dipper. The four stars of the "Bowl" original: Kui (魁) constitute the "Rotating Engine," while the three stars of the "Handle" original: Shao (杓) constitute the "Jade Transverse." The Correct Meanings A classic commentary states: The Rotating Engine has a diameter of 8 feet An ancient Chinese foot, or chi, approximately 23cm and a circumference of 25 feet. It is decorated with jewels and connected above to the Transverse, which is a horizontal sighting tube 8 feet long with an aperture diameter of 1 inch. Decorated with jade, one looks through the lower end to observe the movements of the stars; this is the Transverse itself. Since the Han dynasty, this has been called the Armillary Sphereoriginal: Huntianyi (渾天儀). A mechanical model of the celestial sphere used to show the motions of the stars and planets.. Its principle is based on the Spherical Heaven Theoryoriginal: Huntianshuo (渾天說). The belief that the universe is like an egg, with the Earth as the yolk in the center., which posits that the Earth resides in the center while the outer periphery remains supported?... as was famously stated by Zu Geng A 5th-century mathematician and astronomer who accurately calculated the volume of a sphere in former times.