Zhu Yu (author)

[3] Although the compass needle was first described in detail by the Chinese scientist Shen Kuo (1031–1095) in his Dream Pool Essays of 1088 AD, he did not specifically outline its use for navigation at sea.

Should anyone die at sea, his property becomes forfeit to the government...The ship's pilots are acquainted with the configuration of the coasts; at night they steer by the stars, and in the day-time by the sun.

They also use a line a hundred feet long with a hook at the end which they let down to take samples of mud from the sea-bottom; by its (appearance and) smell they can determine their whereabouts.

[5] Zhu Yu wrote that ships springing a leak could hardly be repaired from the inside, though; instead the Chinese employed expert foreign divers (people from the "Kunlun Mountains" region) that would dive into the water with chisels and oakum and mend the damage from the outside.

The earliest Chinese compasses were probably not originally invented for navigation, but to harmonize environments and buildings in accordance with the geometric principles of Feng Shui.

It is proved that the earliest Chinese reference recording a magnetic device used as a "direction finder" is in a Song dynasty book dated from 960 to 1279.

Zhu Yu's Pingzhou Table Talks of 1119 AD was a crucial piece of medieval maritime literature, as it was the first book to outline the use of the magnetic-needle compass for navigation at sea.