Keeping in mind that the smartest women were for millennia typically kept from publicly using their intelligence, the smartest person on historical record, in my opinion, is Leonardo da Vinci. There have been many geniuses who mastered only one field, but da Vinci, among other things, was one of the greatest painters, sculptors and architects of all time, a brilliant engineer, far ahead of his time in anatomy and he anticipated, in his famous notebooks, the construction of helicopters, submarines, mechanical computers and humanoid robots as well. He also thought that a projectile could orbit the earth and so was thinking along the same lines as Kepler and Newton and he would have invented the telescope had not some ignorant people destroyed the mirrors he was building in the belief that they captured souls. If versatile genius is the measure of cleverness, then there is no one on record comparable with Leonardo da Vinci. He even composed a piece of music (based on the sample I heard, a very good one).

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"Some people complain about the system. The system is not good, so they can't do anything. It's an excuse. Freedom is in your heart." (Jin Xing)