Chapter 4, Part 7 - Chuang Tzu

Tzu-ch'i of Nan-po was wandering around the Hill of Shang when he saw a huge tree there, different from all the rest. A thousand teams of horses could have taken shelter under it and its shade would have covered them all. Tzu-ch'i said, "What tree is this? It must certainly have some extraordinary usefulness!"

But, looking up, he saw that the smaller limbs were gnarled and twisted, unfit for beams or rafters, and looking down, he saw that the trunk was pitted and rotten and could not be used for coffins. He licked one of the leaves and it blistered his mouth and made it sore. He sniffed the odor and it was enough to make a man drunk for three days. "It turns out to be a completely unusable tree," said Tzu-ch'i, "and so it has been able to grow this big. Aha ! - it is this unusableness that the Holy Man makes use of!"

The region of Ching-shih in Sung is fine for growing catalpas, cypresses, and mulberries. But those that are more than one or two arm-lengths around are cut down for people who want monkey perches; those that are three or four spans around are cut down for the ridgepoles of tall roofs;", and those that are seven or eight spans are cut down for the families of nobles or rich merchants who want side boards for coffins. So they never get to live out the years Heaven gave them, but are cut down in mid-journey by axes.

This is the danger of being usable. In the Chieh sacrifice," oxen with white foreheads, pigs with turned-up snouts, and men with piles cannot be offered to the river. This is something all the shamans know, and hence they consider them inauspicious creatures. But the Holy Man for the same reason considers them highly auspicious.
~ Burton Watson translation via Terebess Asia Online ~

Go here to read the introductory post to the chapters of the Book of Chuang Tzu.