From A. J. Jacobs's The Know It All:

This Middle Eastern potentate called a meeting of the wise men in his kingdom, and he said, "I want you to gather all the world's knowledge together in one place so that my sons can read it and learn."  The wise men went off, and after a year, they came back with twenty-five volumes of knowledge.  The potentate looked at it and he said, "No.  It's too long.  Make it shorter."  So the wise men went off for another year and they came back with one single volume.  The potentate looked at it and said, "No.  Still too long."  So the wise men went off for another year.  When they came back, they gave the potentate a piece of paper with one sentence on it.  A single sentence.  You know what the sentence was?

This too shall pass.

A. J. Jacobs was reading the Encyclopedia Britannica when he heard that story.  He writes that the encyclopedia bears it out.