The Chinese characters 'san' (山) and 'o' (王) are both composed of three straight lines and one line that crosses them, and this pictographic design was associated with the basic principle of Tendai Sect, or Sandai Sokuitsu (three truths taken as one single principle), for proliferation of the teachings.
また、「山」の字も「王」の字も、三本の線と、それを貫く一本の線からなっており、これを天台宗の思想である三諦即一思想と結びつけて説いた。