In the manuscript On Burning Mirrors and Lenses, ibn Sahl used the law to derive lens shapes that focus light with no geometric aberrations.[89] According to Jim al-Khalili, the law should be called ibn Sahl's law.[90] Vertical-axle windmill: A small wind wheel operating an organ is described as early as the 1st century AD by Hero of Alexandria.[91][92] The first vertical-axle windmills were eventually built in Sistan, Persia as described by Muslim geographers.