《徐霞客游记·粤西游日记二十一》
一里，总有延伸而过的山脊横断在两面山崖间，共越过三条山脊，大约沿山崖向上延伸了六里。
一里，辄有过脊横断两崖间，凡渡三脊，约循崖上者共六里焉。
About a third of a mile farther, a ridge of mountains stretched across the intervals of two precipices, which having crossed three of, continued upwards by the precipice, about two miles.