“You don’t try and buy businesses worth $83 million for $80 million. You leave yourself an enormous margin (of safety). When you build a bridge, you insist it can carry 30,000 pounds, but you only drive 10,000-pound trucks across it. And that same principle works in investing. ” – Warren Buffett on what Benjamin Graham, the father of value investing, meant by having a margin of safety.
Source: The Superinvestors of Graham-and-Doddsville by Warren E. Buffett