From Wikipedia.
The poke bonnet or a hat that frames and encloses the face in the same manner has arrived in this 1819 Stirnbrand portrait of Ekaterina Pavlovna who wears it above a high enclosing neckline with fraise.
Keywords: 1819, Stirnbrand, Catherine Pavlovna, Grand Princess, Queen, Romanov family, Württemberg family, Russian, curly coiffure, feathered bonnet, bows, high enclosing neckline, fraise, lace, epaulettes, long tight sleeves, Empire waistline, close skirt, necklace, wrap