The modern Chinese calligraphy set is comprised of the brush, ink, paper, and inkstone. Collectively they are known as the Four Treasures of the Study. In Chinese calligraphy, the traditional writing instrument is the brush. The common brush has a bamboo body and a head of weasel fur or fine chicken feathers. Inkstones in their simplified form are stone mortar used to grind the rods of ink, and hold ink after the water has liquefied the fine ink powder. Chinese calligraphy paper is a special type of paper which differs from common writing paper. In China, this paper is called Xuanzhi, and is traditionally made in the province of Anhui. The Four Treasures of the Study is the essential for every calligrapher.