I remember reading an article or blog post about a mental calculator who was being tested with people asking them to calculate integer roots of large numbers. The testers snuck in a number that had an irrational root, and the mental calculator said something like "that number doesn't feel right" and got annoyed.

Or something like that. This is a very vague memory and I could easily have gotten the details wrong.

Market resolves based on whether anyone provides me with a link to the story before close.