Arthur Conan Doyle,
Memoirs of Sherlock Holmes — Adventure XXI: The Greek Interpreter
(1894)
“ Holmes laughed at my suggestion. "My dear Watson," said he, "I cannot agree with those who rank modesty among the virtues. To the logician all things should be seen exactly as they are, and to underestimate one's self is as much a departure from truth as to exaggerate one's own powers. When I say, therefore, that Mycroft has better powers of observation than I, you may take it that I am speaking the exact and literal truth." ”
