As a small business owner, you know all about devoting a lot of time to something. You'd think the need for so much attention and work would run counter to the idea that four hours of intellectual work a day maxes out our brains. But according to journalist Oliver Burkeman, researchers studying the schedules of violinists found that while elite performers might rack up an impressive amount of practice, they do it in chunks of four hours or less.

Science might have documented this four-hour maximum fairly recently, but apparently geniuses in a wide range of fields have known it for centuries.

"Charles Darwin worked for two 90-minute periods in the morning, then an hour later on; the mathematician Henri Poincaré from 10am till noon then 5pm till 7pm; the same approximate stretch features in the daily routines of Thomas Jefferson, Alice Munro, John le Carré, and many more," writes Burkeman.