"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, “Readers May Be Divided into Four Classes”