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

Ignorant

Ignorant as a pig is of the side pocket of a pool table.
—Anonymous

Ignorant as a bookseller.
—Samuel Taylor Coleridge

As invincibly ignorant as a town-fop judging of a new play.
—John Dryden

Ignorant as a Tripoline ambassador, or an envoy from Mujac.
—Oliver Goldsmith

Ignorant as a raw kitchen wench.
—George Meredith

The ignorant person is like a cock out of season, which crows at midnight.
—Osmanli Proverb

Ignorant as dirt.
—William Shakespeare

Ignorant as a child.
—Henry D. Thoreau