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

Stubborn

Stubborn as a mule.
—Anonymous

As stubborn as the will of kings.
—Ambrose Bierce

As stubborn as Muirkirk iron.
—James Hogg

Stubborn as a stone.
—Victor Hugo

Stubborn people are like reproaches, and we have a right to laugh at them.
—Victor Hugo

Stubborn as the Rocky Mountains.
—Richard Le Gallienne

Stubborn as an elephant’s leg, no bending in her.
—William Rowley

More stubborn-hard than hammer’d iron.
—William Shakespeare