“No man can comfortably do without three copies of a book.”
"Nineteenth-century English collector Richard Heber justified his insatiability with impeccable logic: "Why, you see, sir, no man can comfortably do without three copies of a book. One he must have for a show copy, and he will probably keep it at his country-house; another he will require for his own use and reference; and unless he is inclined to part with this, which is very inconvenient, or risk the injury of his best copy, he must needs have a third at the service of his friends."