Windmill
The first windmills had long vertical shafts with rectangle shaped blades. They existed in Persia in the 9th century. There is a story about a windmill and the second caliph Umar (634\644 AD). It is not known if this is a true story. These windmills were made of six to twelve sails. The sails were covered in reed matting or cloth. They were very different from European versions. A similar type of vertical shaft windmill with rectangle blades can also be found in 13th century China. They were used for irrigation.