佛祖統紀 3.151

3.151

若約時則日輪當午。罄無側影（法華開顯。三乘九界咸皆悟入。譬如日輪正午無處不明。是則先照高山寅時也。次照幽谷卯時也。次照平畆辰時也。禺中巳時也。宋嚴觀二法師。與太史何承天。論中邊之國。依周禮。用一尺五寸上圭。立八尺之表。夏至午時以測日景。猶有餘陰。知此方非中國也。天竺此時無餘陰。知為中國也。地上寸影天上萬里。今言側影者餘陰也。影古作景。晉葛洪字苑。始改作影）。

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.)