Caltrop

And as she lookt about, she did behold,
How over that same dore was likewise writ,
Be bold, be bold, and every where Be bold,
That much she muz'd, yet could not construe it
By any ridling skill, or commune wit.
At last she spyde at that roomes upper end,
Another yron dore, on which was writ,
Be not too bold; whereto though she did bend
Her earnest mind, yet wist not what it might intend.
Spenser