Juan You Za Lu (Miscellaneous Records of Exhaustive Travels) by Zhang Shizheng (Northern Song Dynasty)

In the Northern Song Dynasty (AD 960-1127), Zhang Shizheng wrote in Juan You Za Lu that "It is said in Miscellaneous Records of Lingnan that 'On the beach, there is a pond, from which the locals mined pearls for sale.' I once took an official post in Zhirongzhou State, which is near Hefu. Therefore, I am well aware of the fact. There are a dozen pearl ponds in the sea, not on the sandy beaches... Duanwangchi Pond, situated on the demarcation line with Jiaozhi, produces large pearls. When the barbarians of the south went to mine the pearls, they were more often than not robbed by the people of Jiaozhi. Pearls were found in seas hundreds of chi's deep and often guarded by large fish. Even the barbarians dared not venture close." The description tells the Song-Dynasty fishermen mining and selling pearls in the South China Sea.