佛祖統紀 48.42

48.42

In the fourth year, an imperial decree promulgated the newly created Mongolian script throughout the realm. Earlier, the emperor had commanded Imperial Preceptor 'Phags-pa to create a new Mongolian script. Its characters numbered only a little over a thousand, with forty-one letters. For those that were combined and linked to form characters, there were the rules of rhyme articulation; for those formed by combining two, three, or four sounds, there were the rules of phonetic rhyme; and the essential principle was to rely on harmonious sounds. At this point, an imperial decree promulgated it.