《山海经·海经·海内经》
在南海以内，黑水青水流经的地方，有一种树木名叫若木，而若水就从若木生长的地底下发源。
南海之外，黑水青水之间，有木名曰若木，若水出焉。
In the area within the Southern Sea, where Hei Shui (黑水) and Qing Shui (青水) flow, there is a type of tree called Ruo Mu (若木). And Ruo Shui (若水) originates from the ground under the Ruo Mu tree.