R. Austin Freeman, The Red Thumb Mark — Chapter XIII (1924)
“ In my case the habit is one that has been deliberately cultivated—not in reference to letters only, but to everything that comes into my hands—the habit of allowing nothing to pass without a certain amount of conscious attention. The observant man is, in reality, the attentive man, and the so-called power of observation is simply the capacity for continuous attention. As a matter of fact, I have found in practice, that the habit is a useful one even in reference to letters; more than once I have gleaned a hint from the outside of a letter that has proved valuable when applied to the contents. ”
