From Spelling for the Grades, 1926.

Car doodles in Expressing Yourself by Wade, Blossom & Eaton, 1938.

A doodle on a blank page of Foundations of Botany by Joseph Bergen, 1901.

Doodles on the endpapers of Treasure Island by Robert Louis Stevenson, 1926.

Note the occult equation above the fingertips: skull and bones minus x divided by plus equals upside down semicolon colon upside down exclamation point upside down question mark. (Actually that colon may be upside down, too ... difficult to tell.)

From Colorado College's 1902 yearbook.

Doodles made while not listening to a church sermon.  From Together, 1965.

From The Queer Beasts by Arthur Acland, 1919.

A doodle on the title page of God's Smile by Julius Magnussen, 1920.

Here's the serpentine squiggle from Tristram Shandy, translated into French by Honoré de Balzac for inclusion in his novel La Peau de Chagrin and then converted back into English by Balzac's translator Ellen Marriage.  See our collection of this squiggle's transliterations here.

Here's a basket of eggs from Old-Time Schools and School-Books by Clifton Johnson, 1904.

Thanks to Malo for the doodle!