Doctrine of the Mean
The original sources include the Blue Cliff Record, The Gateless Gate, the Sutras, The Analects, The Great Learning, The Doctrine of the Mean, writings by Mencius, Laozi and Zhuang Zhou, and the poetry of Hanshan, Tao Yuanming, Du Fu, Li Bai, and Bai Juyi, among others. Tōyō arranged the writings in order of length, from single- to eight-character expressions, interspersing parallel verses of five through eight characters.