a type of chair used in medieval England and later France. Usually formed in a high-grade leather or red velvet, it was placed by the front door of an estate or home for use by a gatekeeper servant who was in charge of screening guests and visitors. This was necessary since the door knocker might not be heard throughout the house.
Since there were often cold breezes near a front door, the chair was designed to envelop and keep the servant relatively warm in his task of remaining at the door for long periods. It is best described as a hollowed-out egg shape, very high and enclosed back, standing on end, four legs, with handrests and usually with a notch for a lantern at the side, allowing the person to sink back into it out of the wind and await visitors' knocks.
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On the main terrace, [he] sat huddled in a porter's chair.
Agatha Christie. And Then There Were None. p.85 (1939)
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seated in two black horsehair porter's chairs, one on each side of the fire-place, the superannuated Mr. and Mrs. Smallweed while away the rosy hours.
Charles Dickens. Bleak House (1853)
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he found Mr Lillyvick and Miss Petowker; the four Miss Kenwigses on their form of audience; and the baby in a dwarf porter's chair with a deal tray before it, amusing himself with a toy horse without a head;
Charles Dickens. The Life and Adventures of Nicholas Nickleby