Woolsack
2 of the 7 encyclopedias on this shelf carry an entry for Woolsack. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
the name given to the seat of the Lord Chancellor of of England E in the House of Lords, whose essential portion is a large square bag of wool without either back or arms, and covered with red cloth, the whole forming a kind of cushioned ottoman , standing near the center of the chamber. It is believed that woolsacks were placed in the House of Lords in the time of Edward III. to remind the peers of the importance of England's staple trade. An Act of Henry VIII. directs that the Lord Chancellor, Lord Treasurer, or other high officer shall sit and be placed at the uppermost part of the sacks in the said Parliament chamber, either there to sit on one form or on the uppermost sack. D'Ewes says the Lord Keeper sat on the woolsack in 1559 when her majesty (Queen Elizabeth) was absent; the other woolsacks being as now allotted to the other judges. In 1621 it was declared in the standing orders of the House of Lords that "the Lord Chancellor sitteth on the Woolsack as Speaker to the House"-i. e. not in his judicial capacity.
Aiton's Encyclopedia (1910)
in British history, a cushion stuffed with wool on which the lord chancellor sits in the House of Lords . It is a large square bag of wool. The seat is without back or arms. It is covered with green cloth. In his Essay on Warren Hastings Macaulay says: "He was then called to the bar, was informed from the woolsack that the lords had acquitted him, and was solemnly discharged." In his Dictionary of Phrase and Fable Brewer makes the seemingly fanciful statement that an act of Parliament was passed in the reign of Queen Elizabeth to forbid the exportation of wool, and that woolsacks were provided as seats for the judges in the House of Peers in order that this source of national wealth might be kept in mind.