During the Mongol epoch a large number of the Chinese scholars withdrew from official life. They lived in retirement among their friends, and devoted themselves mainly to the pursuit of the art of poetry, which had been elaborated in the Later Sung epoch, without themselves arriving at any important innovations in form. Their poems were built up meticulously on the rules laid down by the various schools; they were routine productions rather than the outcome of any true poetic inspiration. In the realm of prose the best achievements were the "miscellaneous notes" already mentioned, collections of learned essays. The foreigners who wrote in Chinese during this epoch are credited with no better achievements by the Chinese historians of literature. Chief of them were a statesman named Yeh-lü Ch'u-ts'ai, a Kitan in the service of the Mongols; and a Mongol named T'o-t'o (Tokto). The former accompanied Genghiz Khan in his great campaign against Turkestan, and left a very interesting account of his journeys, together with many poems about Samarkand and Turkestan. His other works were mainly letters and poems addressed to friends. They differ in no way in style from the Chinese literary works of the time, and are neither better nor worse than those works. He shows strong traces of Taoist influence, as do other contemporary writers. We know that Genghiz Khan was more or less inclined to Taoism, and admitted a Taoist monk to his camp (1221-1224). This man's account of his travels has also been preserved, and with the numerous European accounts of Central Asia written at this time it forms an important source. The Mongol Tokto was the head of an historical commission that issued the annals of the Sung dynasty, the Kitan, and the Juchên dynasty. The annals of the Sung dynasty became the largest of all the historical works, but they were fiercely attacked from the first by Chinese critics on account of their style and their hasty composition, and, together with the annals of the Mongol dynasty, they are regarded as the worst of the annals preserved. Tokto himself is less to blame for this than the circumstance that he was compelled to work in great haste, and had not time to put into order the overwhelming mass of his material.