Polehead

The sketch is from a photograph, and shows one of these old type of vessels before a light wind, with a small square topsail set upon the polehead of her single lofty spar.

Source: wiktionary

She was painted in encaustic purple, with a scarlet forecastle; her stern canopy was of laminated and gilded plates, with a carved lantern hanging from a scroll, and silk curtains to conceal the General's couch; her sails, reefed to the yard, were of purple silk; and at her polehead flew the purple flag -- the signal for action.

Source: wiktionary

Thus the mizen-mast is devoid of a mizen-topgallant, despite a topmast polehead long enough to carry one.

Source: wiktionary

They are not seen again until the camping-ground for the night is reached, when the four tents will be found pitched ready for us, with English and American flags flying at their poleheads.

Source: wiktionary