佛祖統紀 3.151

3.151

If considered according to time, the sun is directly at zenith, and there are completely no oblique shadows. (In the Lotus's opening and revealing, the three vehicles and nine realms all awaken and enter. It is like the sun disk at exact noon, with nowhere unillumined: first illuminating the high mountains is the yin hour; next illuminating the deep valleys is the mao hour; next illuminating the flat fields is the chen hour; the late morning is the si hour. In the Song dynasty, the two Dharma masters Yan and Guan debated with the Grand Astrologer He Chengtian about central and border countries: relying on the Rites of Zhou, they used an upper jade tablet of one foot five inches and erected an eight-foot gnomon to measure the sun's shadow at noon on the summer solstice; there was still remaining shadow, so they knew that this region was not the Central Country. In Tianzhu at this time there is no remaining shadow, so it is known to be the Central Country. An inch of shadow on the ground corresponds to ten thousand li in heaven. What is here called "oblique shadow" is the remaining shadow. "Ying" [shadow] was anciently written "jing"; it was first changed to "ying" in the Ziyuan by Ge Hong of the Jin dynasty.)