Taizu also displayed a strong interest in science and technology. He employed the Imperial Workshop to support such projects as Zhang Sixun's hydraulic-powered armillary sphere (for astronomical observation and time-keeping) that used liquid mercury instead of water (because liquid mercury would not freeze during winter). Emperor Taizu was also quite open-minded in his affairs, especially with those perceived as foreigners: he appointed the Arab Muslim Ma Yize (910–1005) as the chief astronomer of the Song court. For receiving envoys from the Korean kingdom of Goryeo alone, the Song court had roughly 1,500 volumes written about the nuanced rules, regulations, and guidelines for their reception. The Song also sent envoys abroad, such as Wang Yande (939–1006), who was sent as an official envoy to the Uyghur-Turkic city of Gaochang in 981, then under Kara-Khanid control. From the 2nd century onwards, ancient Chinese histories even record that embassies of the Roman Empire ("Daqin") and Byzantine Empire ("Fu lin") arrived in China. As recorded in the "History of Song" and "Wenxian Tongkao", the last known arrival of Byzantine envoys came in 1081, apparently sent by Michael VII Doukas to the court of Emperor Shenzong of Song. However, the "History of Yuan" records that a Byzantine man served as an astronomer and physician at the court of Kublai Khan during the subsequent Yuan dynasty, and in 1371 the Hongwu Emperor of the Ming dynasty sent an alleged Byzantine merchant (who was likely Nicolaus de Bentra, Archbishop of Khanbaliq) to inform the Byzantine ruler of the founding of the new dynasty.