The Moving Finger writes; and, having writ,
Moves on: nor all thy Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it
-- Omar Khayyam (from Edward Fitzgerald's famous translation of Khayyam's Rubaiyat)
One of my favorite parts of this verse (besides, you know, being an absolutely perfect four-line poem with an absolutely affecting image) is how metrically complex the first two lines are. I'm going to go into this, but first look at the last two lines:
Shall lure it back to cancel half a Line,
Nor all thy Tears wash out a Word of it