Tian yuan shu

The Tianyuanshu was explained in the writings of Zhu Shijie (Jade Mirror of the Four Unknowns) and Li Zhi (Ceyuan haijing), two Chinese mathematicians during the Mongol Yuan dynasty.

[1] However, after the Ming overthrew the Mongol Yuan, Zhu and Li's mathematical works went into disuse as the Ming literati became suspicious of knowledge imported from Mongol Yuan times.

Zhu's text Suanxue qimeng was deciphered and was important in the development of Japanese mathematics (wasan) in the 17th and 18th centuries.

Tian yuan shu means "method of the heavenly element" or "technique of the celestial unknown".

It is a positional system of rod numerals to represent polynomial equations.