In "Dream Pool Essays" Shen Kuo Provides the Earliest Description of the Compass

In 1086 Chinese scholar and scientist of the Song Dynasty Shen Kuo (Shen Gua) wrote Dream Pool Essays while virtually isolated on his lavish garden estate near modern-day Zhenjiang, in the southwest of Jiangsu province.

Dream Pool Essays contained the earliest description of the principle of the compass—magnetizing a needle by rubbing its tip with lodestone, hanging the magnetic needle with one single strain of silk with a bit of wax attached to the center of the needle. Shen Kua pointed out that the needle prepared this way sometimes points south, sometimes points north.