" You can find it on almost any tree. As we made our way through the forest, it was literally raining rubber juice. Our clothes were full of it. The Congo has so many tributaries that a well-organized company can easily extract a few tons of rubber per year here. You only have to sail up such a river and the branches with rubber hang almost up to your ship. (In a Letter to King Leopold II of the Belgians) "

― Henry M. Stanley