L. Frank Baum

“ And who, having the power, could also have an object in defying the wisest and most talented Sorceress the world has ever known?
Glinda thought over the perplexing matter for a full hour, at the end of which time she was still puzzled how to explain it. But although her instruments and chemicals were gone, her knowledge of magic had not been stolen, by any means, since no thief, however skillful, can rob one of knowledge, and that is why knowledge is the best and safest treasure to acquire. ”

“ It was considered a great honor to be allowed to serve the good Sorceress, whose arts of magic were used only to benefit the Oz people. Glinda was Ozma's most valued servant, for her knowledge of sorcery was wonderful, and she could accomplish almost anything that her mistress, the lovely girl Ruler of Oz, wished her to. ”