of a rope coiled about a tree." Along with his colleague Wei Pu in the Bureau of Astronomy, Shen Kuo planned to plot out the exact coordinates of planetary and lunar movements by recording their astronomical observations three times a night for a continuum of five years. The Song astronomers of Shen's day still retained the lunar theory and coordinates of the earlier Yi Xing, which after 350 years had devolved into a state of considerable error. Shen criticized earlier Chinese astronomers for failing to describe celestial movement in spatial terms, yet he did not attempt to provide any reasoning for the motive power of the planets or other celestial movements. Shen and Wei began astronomical observations for the Moon and planets by plotting their locations three times a night for what should have been five successive years. The officials and astronomers at court were deeply opposed Wei and Shen's work, offended by their insistence that the coordinates of the renowned Yi Xing were inaccurate. They also slandered Wei Pu, out of resentment that a commoner had expertise exceeding theirs. When Wei and Shen made a public demonstration using the gnomon to prove the doubtful wrong, the other ministers reluctantly agreed to correct the lunar and solar errors. Despite this success, they eventually dismissed Wei and Shen's tables of planetary motions. Therefore, only the worst and most obvious planetary errors were corrected, and many inaccuracies remained. Movable type printing Shen Kuo wrote that during the Qingli reign period (1041–1048), under Emperor Renzong of Song (1022–1063), an obscure commoner and artisan known as Bi Sheng (990–1051) invented ceramic movable type printing. Although the use of assembling individual characters to compose a piece of text had its origins in antiquity, Bi Sheng's methodical innovation was something completely revolutionary for his time. Shen Kuo noted that the process was tedious if one only wanted to print a few copies of a book, but if one desired to make hundreds or thousands of copies, the process was incredibly fast and efficient. Beyond Shen Kuo's writing, however, nothing is known of Bi Sheng's life or the influence of movable type in his lifetime. Although the details of Bi Sheng's life were scarcely known, Shen Kuo wrote: When Bi Sheng died, his fount of type passed into the possession of my followers (i.e. one of Shen's nephews), among whom it has been kept as a precious