Compass (sinan / magnetic needle)

Timeline

1. 1044Kaifeng, Northern Song · KaifengThe Wujing Zongyao records making a fish-shaped thin iron sheet, heating it red and quenching it in water to magnetize it; floated in a bowl of water it pointed north-south, letting soldiers orient themselves on dark nights or when lost—a thermoremanent guiding device.
2. c. 1086–1088Mengxi Garden, Runzhou · ZhenjiangShen Kuo's Dream Pool Essays records magnetizing steel needles by rubbing them with lodestone, floating them on water, placing them on a fingernail, or suspending them by a thread; it also notes the needle often deviates slightly east of true south, the earliest clear written record of magnetic declination in the world.
3. c. 1081–1090Northern Song northwestern frontier (Song-Xia war front) · NorthwestThe magnetic-needle compass was easier to carry and read than the guiding fish, gradually replacing the thermomagnetic guiding fish in Northern Song campaigns against Western Xia in the northwest and in long-distance marches, laying the technical foundation for later maritime compasses.