Navigation By Dead Reckoning

"In the midst of this chopping sea of civilized life, such are the clouds and storms and quicksands and thousand-and-one items to be allowed for, that a man has to live, if he would not founder and go to the bottom and not make his port at all, by dead reckoning, and he must be a great calculator indeed who succeeds." -Henry David Thoreau, "Where I Lived, What I Lived For," in Walden, 1854.