《淮南子·汜论训》
黄河流域的平原地带，尽管小土丘多得数都数不过来，但这一地带仍不失平坦；水流急得会激起波浪，有时浪头高达数尺之高，但河水仍不失平静。
河上之丘冢，不可胜数，犹之为易也。水激兴波，高下相临，差以寻常，犹之为平。
Although there are numerous small hills in the plains of the Yellow River Basin, the area is still flat; the water flow is so fast that it can cause waves, and sometimes the waves can be several feet high, but the river is still calm.