《徐霞客游记·闽游日记前》
凡是河流，源流都很微小，不能浮起竹筏，如果通航后，到下游反而受阻，只有黄河的三门集津，船只不能上下。
凡水惟滥觞发源之始，不能浮槎竹筏，若既通，而下流反阻者，止黄河之三门集津，舟不能上下。
All rivers have very small sources and cannot float rafts. If they are navigable, they will be blocked when they reach the lower reaches. Only the Sanmen J津 of the Yellow River can not go up and down the boat.