Strong and highly durable Japanese red pines, each of which was 23.6 meter-long and the diameter of which was one meter-long, were necessary; Koryo of Daibutsu-den Hall of Todai-ji Temple were to be 23.1 meter, three times as long as the space between two pillars, which was 7,7 meters; the roof was to be 3020 tons.
東大寺大仏殿の虹梁は、柱の間隔7.7メートル（2丈5尺4寸）の3倍すなわち23.1メートルの長さを持ち、3020トンの屋根を支える必要があることから、長さ23.6メートル（13間）、直径1メートル（3尺）で強度があり耐久性の高いアカマツが求められた。