Which Chinese invention for navigation was first described in a Song dynasty text?

The magnetic compass was the Chinese navigation invention first described in a Song dynasty text. The scientist and statesman Shen Kuo described a magnetized needle in his 1088 work, the Dream Pool Essays.

Chinese knowledge of directional devices was older than Shen Kuo’s account. The 1044 military compendium Wujing Zongyao described a heated, fish-shaped iron object that acquired magnetism and floated in water as a directional aid. This was an early thermoremanent compass, rather than the later familiar needle compass.

Shen Kuo explained that steel needles could be magnetized by rubbing them with lodestone. He also noticed magnetic declination: the needle did not point exactly toward true north. His observations helped make the compass more useful for practical navigation. Zhu Yu’s 1119 Pingzhou Table Talks provides the first clear record connecting a magnetic needle compass with seafaring.

The sextant and astrolabe are different instruments associated with astronomical measurement and navigation. The rudder steers a vessel but does not indicate direction. Another common mistake is treating Shen Kuo’s description as the first invention of magnetism; it was instead a crucial early written description of the magnetic needle compass.