Definition of "woolsack"

We shall never beat the French says one, why truly replied I, 'tis like kicking at a Woolsack—there is perpetual Resistance made, & a strange Elasticity […] .

1794 January 23, Hester Lynch Piozzi, Thraliana

“O rare-painted portrait!” exclaimed Rashleigh, when I was silent—“Vandyke was a dauber to you, Frank. I see thy sire before me in all his strength and weakness, loving and honouring the King as a sort of lord mayor of the empire, or chief of the board of trade;—venerating the Commons, for the acts regulating the export trade;—and respecting the Peers, because the Lord Chancellor sits on a wool-sack.”

1817 December 31 (indicated as 1818), [Walter Scott], “[XI]”, in Rob Roy. […], volume I, Edinburgh: […] James Ballantyne and Co. for Archibald Constable and Co. […]; London: Longman, Hurst, Rees, Orme, and Brown, pages 265–266

On entering the House, he is described to have appeared abashed and pale: he passed the woolsack without looking round, and advanced to the table where the proper officer was attending to administer the oaths.

1830, John Galt, The Life of Lord Byron‎

Well, Dick," rejoined Sir Wynston, merrily, "if both are to be fulfilled, or neither, I trust you may never sit upon the woolsack of England."

1895, J. Sheridan Le Fanu, The Evil Guest‎

But when the Lord Chancellor left the woolsack to congratulate him, and with a smiling face extended his hand, the embittered young peer bowed coldly and stiffly, and simply held out two or three of his fingers,--an act of impudence for which there was no excuse.

1902, John Lord, Beacon Lights of History, Volume XIII‎