《徐霞客游记·粤西游日记二十六》
又行二里，就见平坦的原野在西边到了尽头，有两座石峰隔在南北两山之间，好像把守关口的样子。
又二里，则平畴西尽，有两石峰界南北两山间，若当关者。
After another two li, the flat wilderness reaches its end to the west, and there are two stone peaks separating the mountains to the north and south as if they were gatekeepers.