Zhoubi Suanjing

周髀算經 (Arithmetical Classic of the Gnomon and the Circular Paths of Heaven)

Anonymous, composite · c. 50 BC - AD 100 · North China (composition place unattested) (China) · science

The heavens can be measured with a gnomon's shadow and a right triangle, so astronomy and geometry are really one discipline, with the Pythagorean relationship stated as a practical surveying tool rather than an abstract proof.