Legend gives credit for developing silk to a Chinese empress, Leizu (Hsi-Ling-Shih, Lei-Tzu). The Xia Dynasty is the first dynasty in China to be described in ancient historical chronicles such as Bamboo Annals, Classic of History and Records of the Grand Historian. The dynasty was established by the legendary Yu the Great after Shun, the last of the Five Emperors gave his throne to him. The earliest bronze artifacts have been found in the Majiayao culture site (between 3100 and 2700 BC),[19][20] and from then on, the society gradually grew into the Bronze Age. The Shang Dynasty ruled in the Yellow River valley in the second millennium BC. The classic account of the Shang comes from texts such as the Classic of History, Bamboo Annals and Records of the Grand Historian. The earliest surviving examples of writing in China are inscriptions on so-called "oracle bones", tortoise plastrons and ox scapulae used for divination. Although the Zhou Dynasty lasted longer than any other dynasty in Chinese history, the actual political and military control of China by the Ji family lasted only until 771 BC, a period known as the Western Zhou. During this reign the dynasty reaches the peak of its power and territorial control. The capital Hao is sacked. Zhou rule continues from a new capital to the east. Central control under the Eastern Zhou is weak and local rulers emerge. Chinese coins were produced continuously for around 2,500 years by casting in moulds, rather than being struck with dies as with most western coins. Laozi was a philosopher of ancient China, best known as the author of the Tao Te Ching. His association with the Tào Té Chīng has led him to be traditionally considered the founder of philosophical Taoism. Confucius was a Chinese teacher, editor, politician, and philosopher of the Spring and Autumn Period of Chinese history. The philosophy of Confucius emphasized personal and governmental morality, correctness of social relationships, justice and sincerity. Wu was considered one of the greatest emperors in Chinese history as the Chinese empire reaches its greatest extent. Sima Qian completed the first systematic history of China from c. 2600 BC until his own times.