E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
We Three.
Did you never see the picture of We Three? asks Sir Andrew Aguecheeknot meaning himself, Sir Toby Belch, and the clown, but referring to a public-house sign of Two Loggerheads, with the inscription, We three loggerheads be, the third being the spectator.