I am but mad north-north-west: when the wind is southerly I know a hawk from a handsaw.

– William Shakespeare

Hamlet, Act 2, Scene 2. Hamlet says to Rosencrantz and Guildenstern that he is more often sane than mad, and that he knows a hawk from its prey – a heronshaw or heron. He is warning that he can distinguish his enemies from his friends, a pointed comment to "friends" Rosencrantz and Guildenstern.