Many useful and valuable books lie buried in shops and libraries, unknown and unexamined, unless some lucky compiler opens them by chance, and finds an easy spoil of wit and learning. – Samuel Johnson, 1760

But I have long thought that if you knew a column of advertisements by heart, you could achieve unexpected felicities with them. You can get a happy quotation anywhere if you have the eye. – Oliver Wendell Holmes, Jr., 1923, quoted in Holmes-Laski Letters: The Correspond

I am now to offer some thoughts upon that sameness or familiarity which we frequently find between passages in different authors without quotation. This may be one of three things either what is called Plagiarism, or Imitation, or Coincidence. – James Boswell, “The Hypochondriack,” No.XXII, 1779