Try to do the impossible, as in Getting that bill through the legislature is the same as trying to square the circle. This idiom alludes to the impossibility of turning a circle into a square. John Donne may have been the first to use it (Sermons, 1624): “Go not thou about to square either circle (God or thyself).”
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.