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

Tough

Tough as any bough.
—Anonymous

Tough as leather.
—Anonymous

Tough as nails.
—Anonymous

Tough as shoe-leather.
—Anonymous

As tough as whit-leather.
—Anonymous

Tough as old hickory.
—J. R. Bartlett’s Dictionary of Americanisms

Tough as an India-rubber ball.
—Charlotte Brontë

Tough as a Cape Cod fisherman.
—Robert Edgren

Tough as a telegraph wire.
—Richard Le Gallienne