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.
-Samuel Taylor Coleridge, poet, critic (1772-1834)
