ink. Other than stone, inkstones are also manufactured from clay, bronze, iron, and porcelain. The device evolved from a rubbing tool used for rubbing dyes dating around 6000 to 7000 years ago. The earliest excavated inkstone is dated from the 3rd century BC, and was discovered in a tomb located in modern Yunmeng, Hubei. Usage of the inkstone was popularized during the Han Dynasty. Inoculation, treatment of smallpox: As Europeans would not begin to develop vaccinations for smallpox until 1796, historical Chinese records show that Chinese physicians have been inoculating against the same disease hundreds of years earlier. The British scientist, sinologist, and historian Joseph Needham states that a case of inoculation for smallpox may have existed in the late 10th century during the Song Dynasty (960–1279), yet they rely on a book Zhongdou xinfa (種痘心法) written in 1808 by Zhu Yiliang for this evidence. Wan Quan (1499–1582) wrote the first clear reference to smallpox inoculation in his Douzhen xinfa (痘疹心法) of 1549. The process of inoculation was also vividly described by Yu Chang in his Yuyi cao (寓意草), or Notes on My Judgment published in 1643, and Zhang Yan in his Zhongdou xinshu (種痘新書), or New book on smallpox inoculation in 1741. As written by Yu Tianchi in his Shadou jijie (痧痘集解) of 1727, which was based on Wang Zhangren's Douzhen jinjing lu (痘疹金鏡錄) of 1579, the technique of inoculation to avoid smallpox was not widespread in China until the reign of the Longqing Emperor (r. 1567 – 1572) during the Ming Dynasty (1368–1644). J Jacob's staff: The Song Dynasty (960–1279) polymath Shen Kuo (1031–1095), an antiquarian who pursued studies of archaeological finds, unearthed an ancient crossbow-like mechanism from a garden in Jiangsu which had on its stock a graduated sighting scale in minute measurements. He wrote that while viewing the whole of a mountain, the distance on the instrument was long, but while viewing a small part of the mountainside the distance was short due to the device's cross piece that had to be pushed further away from the observer's eye, with the graduation starting on the further end. He wrote that if one placed an arrow on the device and looked past its end, the degree of the mountain could be measured and thus its height could be calculated. Shen wrote that this was similar to mathematicians who used right-angled triangles to measure height. British scientist, sinologist,