Because texts drifted and factions edited them to suit their readings, the state periodically fixed the classics in stone. Between 175 and 183 CE, under Cai Yong's supervision, some 200,000 characters covering seven texts were carved on forty-six stelae at the imperial academy outside Luoyang, precisely so that no one could alter the wording to support a position. These Xiping Stone Classics survive only in fragments. The Kaicheng Stone Classics, completed in 837 under the Tang, cut twelve classics in over 650,000 characters on 114 double-sided tablets; they still stand, in the Stele Forest at Xi'an.
The canon expanded as commentaries were promoted to classic status. The three commentaries on the Spring and Autumn Annals were counted separately, the Rites split into three works, and the Analects, the Classic of Filial Piety, the Erya dictionary and the Mencius were added, giving the Thirteen Classics, the list settled by the Song and printed as a set thereafter.
Mastery of this material was the qualification for office. The imperial examinations tested the classics and their approved commentaries from the Sui and Tang onwards, and after 1313 the Four Books with Zhu Xi's readings took the leading place, with the Five Classics as the field a candidate specialised within. Passing meant reproducing the text and the orthodox interpretation of it under examination conditions, which produced an administrative class sharing one body of memorised reference and a set of assumptions carried in the phrasing itself. The system was abolished in 1905, and with it the direct link between these five books and a career, though the texts remain the backbone of the Chinese literary inheritance.