known textual reference to the use of chopsticks comes from the Han Feizi, a philosophical text written by writer and philosopher Han Fei (c. 280–233 BC) in the 3rd century BC. Chromium, use of: The use of chromium was invented in China no later than 210 BC when the Terracotta Army was interred at a site not far from modern Xi'an; modern archaeologists discovered that bronze-tipped crossbow bolts at the site showed no sign of corrosion after more than 2,000 years, because they had been coated in chromium. Chromium was not used anywhere else until the experiments of French pharmacist and chemist Louis Nicolas Vauquelin (1763–1829) in the late 1790s. Chuiwan: Chuiwan, a game similar to the Scottish-derived sport of golf, was first mentioned in China by Song dynasty writer Wei Tai (fl. 1050–1100) in his Dongxuan Records (東軒錄); it was popular amongst men and women in the Song Dynasty (960–1279) and Yuan Dynasty (1279–1368), while it was popular among urban men in the Ming Dynasty (1368–1644) in much the same way that tennis was for early urban Europeans during the Renaissance (according to Andrew Leibs). In 1282, the writer Ning Zhi published the Book of Chuiwan, which described the rules, equipment, and playing field of chuiwan, as well as included commentary of those who mastered its tactics. The game was played on flat and sloping grassland terrain and—much like the tee of modern golf—had a "base" area where the first of three strokes were played. Civil service examinations: During the Han Dynasty (202 BC – 220 AD), the xiaolian system of recruiting government officials through formal recommendations was the chief method of filling bureaucratic posts, although there was an Imperial Academy to train potential candidates for office and some offices required its candidates to pass formal written tests before appointment. However, it was not until the Sui Dynasty (581–618) that civil service examinations became open to all adult males not belonging to the merchant class (although civil service examinations was a path to social advancement in Imperial Chinese society to candidates regardless of wealth, social status, or family background) and were used as a universal prerequisite for appointments to office, at least in theory. The civil service system was implemented on a much larger scale during the Song Dynasty (960–1279), when an elite core of dynastic-founding and professional families lost their majority in government to a broad strata of