The Splendid Spur by Arthur Quiller-Couch

You are now to be ask'd to pass over the next four weeks in as many minutes: as would I had done at the time! For I spent them in a bitter cold cell in the main tower of Bristol keep, with a chair and a pallet of straw for all my furniture, and nothing to stay my fast but the bread and water that the jailer -- a sour man, if ever there were one -- brought me twice a day.

This keep lies in the northwest corner of the outer ward of the castle -- a mighty tall pile and strongly built, the walls (as the jailer told me) being a full twenty-five feet thick near the foundations, though by time you ascended to the towers this thickness had dwindled to six feet and no more. In shape 'twas a quadrilateral, a little shorter from north to south than from east to west (in which latter direction it measured sixty feet, about), and had four towers standing at the four corners, whereof mine was five fathoms higher than the rest.