How short is a short quote?
As the old saying goes about a woman's skirt, a short quote should be: "long enough to cover the subject and short enough to be interesting."
The most famous short quote is from the Bible: "Jesus wept."
On the other hand, Dr. Martin Luther King's often repeated words can also be considered a short quote:
"I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character."