The enormous encyclopedic work in China of the "Four Great Books of Song", compiled by the 11th century during the early Song dynasty (960–1279), was a massive literary undertaking for the time. The last encyclopedia of the four, the "Prime Tortoise of the Record Bureau", amounted to 9.4 million Chinese characters in 1000 written volumes. The 'period of the encyclopedists' spanned from the tenth to seventeenth centuries, during which the government of China employed hundreds of scholars to assemble massive encyclopedias. The largest of which is the Yongle Encyclopedia; it was completed in 1408 and consisted of almost 23,000 folio volumes in manuscript form, the largest encyclopedia in history, until surpassed by Wikipedia in 2007.