Yu Yonghe was a Qing official from Zhejiang who traveled to Taiwan in 1697 on an imperial commission to collect sulfur from the northern hot springs. Over three months he journeyed from Tainan north to the sulfur fields near modern Danshui, recording his observations in a diary. On his return he compiled these notes into Bihai Jiyou (Travels to the Marginal Sea), the earliest and most comprehensive firsthand Chinese-language account of Taiwan. The work describes indigenous communities of the western plains, Kavalan peoples of the northeast, and the nascent Han settler society. Yu's writing blends scholarly observation with literary sensitivity, capturing the alien terrain and unfamiliar customs with curiosity and candor. Bihai Jiyou remains an indispensable primary source for historians of early Qing Taiwan and indigenous Taiwan studies.

• 1697 sulfur mission to Danshui hot-spring fields

• Wrote Bihai Jiyou, earliest firsthand account of Taiwan