"Readers may be divided into four classes:
1.) Sponges, who absorb all that they read and return it in
nearly the same state, only a little dirtied.
2.) Sand-glasses, who retain nothing and are content to get through a book
for the sake of getting through the time.
3.) Strain-bags, who retain merely the dregs of what they read.
4.) Mogul diamonds, equally rare and valuable, who profit by what they read,
and enable others to profit by it also."