Carolyn Wells 
The Mystery of the Sycamore [EPUB ebook] 

As the character of a woman may be accurately deduced from her handkerchief, so a man’s mental status is evident from the way he opens his mail.
Curtis Keefe, engaged in this daily performance, slit the envelopes neatly and laid the letters down in three piles. These divisions represented matters known to be of no great interest; matters known to be important; and, third, letters with contents as yet unknown and therefore of problematical value.
The first two piles were, as usual, dispatched quickly, and the real attention of the secretary centred with pleasant anticipation on the third lot.