《资治通鉴·唐纪·唐纪三十四》
潼关城外先前挖了三条深沟，都是宽二丈，深一丈，过关的人马坠落沟中，很快就填满了沟，后面的人踏着他们得以通过，残兵逃入关内的才八千多人。
关外先为三堑，皆广二丈，深丈，人马坠其中，须臾而满；馀众践之以度，士卒得入关者才八千馀人。
Outside Tongguan City, three deep ditches had been dug in advance, each two zhang wide and one zhang deep. As men and horses attempted to pass, they fell into the ditches, quickly filling them up. Those following walked over their fallen comrades and entered the pass. Only about eight thousand survivors managed to escape into the city.