Wei (386–534) mural at Dunhuang, China, dated 477–499; the latter artwork does not feature the essential collar cushion behind the cross bar, though, while a later Tang Dynasty (618–907) mural of about 851 accurately displays the cushioned collar behind the cross bar. An earlier painting of the Sui Dynasty (581–618) accurately depicted the horse collar as it is seen today, yet the illustration shows its use on a camel instead of a horse. Horse harness, ("trace" or "breast"): Throughout the ancient world, the 'throat-and-girth' harness was used for harnessing horses that pulled carts; this greatly limited a horse's ability to exert itself as it was constantly choked at the neck. A painting on a lacquerware box from the State of Chu, dated to the 4th century BC, shows the first known use of a yoke placed across a horse's chest, with traces connecting to the chariot shaft. The hard yoke across the horse's chest was gradually replaced by a breast strap, which was often depicted in carved reliefs and stamped bricks of tombs from the Han Dynasty (202 BC – 220 AD). Eventually, the horse collar was invented in China, at least by the 5th century. Hygrometer: Prototype hygrometers were devised and developed in the hills during the Western Han dynasty in Ancient China to elucidate mechanisms of long-range meteorological fluctuations. The Chinese used a bar of charcoal and a lump of earth: its dry weight was taken and then compared with its damp weight after being exposed in the air. The differences in weight was used to tally the humidity level. Other techniques were applied using mass to measure humidity such as when the air was dry, the bar of charcoal would be light while the air was humid, the bar of charcoal would be heavy. By hanging a lump of earth and a bar of charcoal on the two ends of a staff separately and adding a fixated lifting string on the middle point to make the staff horizontal in dry air, an ancient hygrometer was made. I India ink: Although named after carbonaceous pigment materials originating from India, Indian ink first appeared in China; some scholars say it was made as far back as the 3rd millennium BC, while others state it was perhaps not invented until the Wei Dynasty (220–265 AD). Inkstone: The inkstone is a stone mortar used in Chinese calligraphy for grinding and mixing