《明史·志·卷六十七》
又转南向东，是保定的边界，经过龙泉、倒马、紫荆、昊王口、插箭岭、浮图峪到沿河口，约一千零七十多里。
又转南而东，为保定界，历龙泉、倒马、紫荆、吴王口、插箭岭、浮图峪至沿河口，约一千七十余里。
Turn south to east again, it is the boundary of Baoding, passing through Longquan, Daom, Zijing, Haowangkou, Chajianling, Futu Valley to Yanhekou, about 1,070 miles.