What is it?" - Optical illusion puzzle

United States, 1860. Fine; some light marginal browning.. A curious optical illusion puzzle in two parts: on the recto, a warped image; on the verso, a tongue-in-cheek riddle in verse. To solve, the viewer must either glean the answer from the riddle's clues or view the image from a specific angle to reveal the image which, in this case, appears to be a well-known Civil War figure. (We suspect the card must be bent a certain way to reveal the image, but have not tried that method for obvious reasons.) The riddle has been signed "Themis". Printed on card (4.5" by 3.25").