Frank J. Wilstach, comp. A Dictionary of Similes. 1916.

Confident

As confident as a bird committing itself to the air or a great fish to the deep.
—Anonymous

Confident as justice.
—George Colman, the Younger

Confident as Hercules.
—William Prynne

Confident as of your own fingers.
—François Rabelais

Confident, as is the falcon’s flight.
—William Shakespeare

Confidence in an unfaithful man in time of trouble is like a broken tooth, and a foot out of joint.
—Old Testament