During the reign of Emperor Xiaozong of Song, the Chinese increased the number of trade missions that would dock at ports throughout the Indian Ocean, where Arab and Hindu influence was once predominant. The Chinese sailed regularly to Korea and Japan in the Far East, westwards towards India and Sri Lanka, and into the Persian Gulf, and the Red Sea. The Chinese were keen to import goods such as rare woods, precious metals, gems, spices, and ivory, while exporting goods such as silk, ceramics, lacquer-ware, copper cash, dyes, and even books. In 1178, the Guangzhou customs officer Zhou Qufei wrote in "Lingwai Daida" of an island far west in the Indian Ocean (possibly Madagascar), from where people with skin "as black as lacquer" and with frizzy hair were captured and purchased as slaves by Arab merchants. As an important maritime trader, China appeared also on geographical maps of the Islamic world. In 1154 the Moroccan geographer Al-Idrisi published his "Geography", where he described the Chinese seagoing vessels as having aboard goods such as iron, swords, leather, silk, velvet, along with textiles from Aden (modern-day Yemen), the Indus River region, and Euphrates River region (modern-day Iraq). He also commended the silk manufactured at Quanzhou as being unparalleled in the world for its quality, while the Chinese capital at Hangzhou was best known throughout the Islamic world for being a major producer of glass wares. By at least the 13th century, the Chinese were even familiar with the story of the ancient Lighthouse of Alexandria since it is described at length by Zhao Rugua, a Southern Song customs inspector of Quanzhou.