Isambard Kingdom Brunel had all the classic traits of the entrepreneur: visionary ideas, total commitment (hanging off bridges, surveying entire railway routes himself), a willingness to risk his own money in projects.
He died at 53, his strength sapped by a punishing self-imposed schedule (lesson en passant: don't forget to take a holiday). Brunel's legacy lives on, but he wasn't immune to concocting the odd balls-up.
Case in point: his plan for an atmospheric railway, with trains propelled by vacuum pipes. The experimental Exeter to Newton Abbot service lasted just a year but Brunel was quick to admit he was wrong and went on to complete such miracles as the Tamar Bridge and the Great Eastern steamship.
Most successful entrepreneurs have their own 'atmospheric railway': remember Sugar's wrinkle electrocuter or Branson's Virgin Cola? Despite their skeletons in the closet, all three are admired for focusing on ideas that worked, instead of agonising over those that didn't.