ago. In I Ching, one of the earliest Chinese writings cites the use of oil in its raw state without refining was first discovered, extracted, and used in China in the first century BCE. In addition, the Chinese were the first to use petroleum as fuel as the early as the fourth century BCE. Pig iron: The earliest pig iron dates to the Zhou Dynasty. By the 5th century, archaeological evidence indicates that pig iron was melted to produce cast iron. In Europe, the process was not invented until the late medieval ages. Pinhole camera: The Greek philosopher Aristotle (384–322 BC) observed that the spaces between the leaves of trees acted as tiny pinholes which cast the image of a partial solar eclipse onto the ground. He also used a metal plate with a small pinhole to project an image of a solar eclipse onto the ground. The ancient Chinese philosopher Mozi (c. 470 BC – c. 391 BC)—founder of Mohism during the establishment of the Hundred Schools of Thought—lived just before the time of Aristotle and it was in his Mojing (perhaps compiled by his disciples) that a pinhole camera was described. The Mojing stated that the "collecting place" (pinhole) was an empty hole "like the sun and moon depicted on the imperial flags," where an image could be inverted at an intersecting point which "affects the size of the image." The Mojing seems to be in line with the Epicurean theory of light traveling into the eye (and not vice versa like in Pythagoreanism), since the Mojing states that the reflected light shining forth from an "illuminated person" becomes inverted when passing through the pinhole, i.e. "The bottom part of the man becomes the top part (of the image) and the top part of the man becomes the bottom part (of the image)." In his Book of Optics (1021), Ibn al-Haytham (965–1039) wrote of his experimentation with camera obscura, which was followed by Song dynasty polymath Shen Kuo (1031–1095), the latter who alluded that the Tang Dynasty (618–907) writer Duan Chengshi (died 863)—in his Miscellaneous Morsels from Youyang—described inverted images of Chinese pagodas. Playing cards: The first reference to the card game in world history dates no later than the 9th century, when the Collection of Miscellanea at Duyang, written by Su E (fl. 880), described the Wei clan (family of Princess Tongchang's husband) of the Tang Dynasty