The Song dynasty witnessed many substantial scientific and technological advances in Chinese history. Some of these advances and innovations were the products of talented statesmen and scholar-officials drafted by the government through imperial examinations. Shen Kuo (1031–1095), author of the Dream Pool Essays, is a prime example, an inventor and pioneering figure who introduced many new advances in Chinese astronomy and mathematics, establishing the concept of true north in the first known experiments with the magnetic compass. However, commoner craftsmen such as Bi Sheng (972–1051), the inventor of movable type printing, were also heavily involved in technical innovations.