《徐霞客游记·滇游日记五》
桥下的溪流，水量是西边流来之水的三倍，所以知道北坞中的水源比东边的水源长远。
桥下溪流，三倍于西来之水，固知北坞之源远于东矣。
The stream under the bridge has three times more water than the one flowing from the west, so it is known that the water source in the northern ravine is longer than the one in the east.