From The Telegraph:
The word 'sinecure’ literally means 'without care’, and by the late 17th century it was already being used for a job with a salary but no real duties. So when Isaac Newton received a letter from the Chancellor of the Exchequer in 1696, offering him the post of Warden of the Mint, he had every reason to think that a sinecure was being dangled in front of him: the salary was £400 a year (four times his pay as a Cambridge professor), and the Chancellor assured him that the work could all be done in his spare time.
Newton accepted, and within a week he had moved out of Cambridge to take up residence in the Tower of London. Perhaps he was looking forward to a life 'without care’, to be devoted to the study of mathematics, physics and his other intellectual passions: alchemy and Biblical interpretation. If so, he was in for a shock when he discovered the scale of the task that awaited him.
More here.
