Ling Wai Dai Da (Notes for the Land beyond the Passes) by Zhou Qufei (Southern Song Dynasty)

In the Southern Song Dynasty (AD 1127-1279), Zhou Qufei recorded in Ling Wai Dai Da that, "The pearl-producing area in Hepu is known as Duanwangchi Pond. Located below an isolated island and ten li off the coast, it is about dozens of meters deep. The local ethnic minorities dive into the water and fetch mussels, which are then cut open for pearls." The narration furnishes a record of fishermen mining pearls in the South China Sea in the Song Dynasty.