梦溪笔谈
In terms of global significance, Zhu Yu's book was the first book in history to mention the use of the mariner's magnetic-needle compass for navigation at sea. 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. The passage from Zhu Yu's "Pingzhou Ketan" relating to the use of the compass states: