I cannot live without brain-work. What else is there to live for? Stand at the window here. Was ever such a dreary, dismal, unprofitable world? See how the yellow fog swirls down the street and drifts across the dun-coloured houses. What could be more hopelessly prosaic and material? What is the use of having powers, doctor, when one has no field upon which to exert them? Crime is commonplace, existence is commonplace, and no qualities save those which are commonplace have any function upon earth.

Arthur Conan Doyle (1859-1930) British writer and physician

Story (1890-02), “The Sign of the Four,” ch. 1 [Holmes], Lippincott’s Monthly Magazine, Vol. 45 (US) / 1 (UK)
    (Source)

The original publication, and Doyle's manuscript (along with many other iterations across media) use "The Sign of the Four" as the title, while others (including the first book publications) use "The Sign of Four." The five-word form is used most commonly in the story, but the four-word form does show up. (More info.)

Published in novel form as The Sign of Four (1890-10).