Bhāskara's wheel was a hypothetical perpetual-motion machine design created around 1150 CE by the

Indian mathematician Indian mathematics emerged in the Indian subcontinent from 1200 BCE until the end of the 18th century. In the classical period of Indian mathematics (400 CE to 1200 CE), important contributions were made by scholars like Aryabhata, Brahmagupta, ...

Bhāskara II Bhāskara II ('; 1114–1185), also known as Bhāskarāchārya (), was an Indian people, Indian polymath, Indian mathematicians, mathematician, astronomer and engineer. From verses in his main work, Siddhānta Śiromaṇi, it can be inferre ...

. The wheel consisted of curved or tilted

spoke A spoke is one of some number of rods radiating from the center of a wheel (the hub where the axle connects), connecting the hub with the round traction surface. The term originally referred to portions of a log that had been riven (split ...

s partially filled with mercury. Once in motion, the mercury would flow from one side of the spoke to another, thus forcing the wheel to continue motion, in constant dynamic equilibrium. Like all perpetual-motion machines, Bhaskara's wheel is a long-discredited mechanism. To truly overbalance the wheel (so that torque in one direction is greater than the other) and cause motion, the radius of the spokes would have to be altered throughout the course of the wheel's motion. This would have to be done actively, thus consuming energy in the process — and so the machine would cease to be a perpetual-motion engine. It's also important to consider the wheel as it moves, as it can be placed into an overbalanced position so that the math makes it appear that there is an overall torque.Magical Machines - The Overbalanced Wheel
/ref> It is perfectly possible for the wheel to exert a motion if it is placed off balance (much in the same way a pendulum will swing if moved out of a perfectly vertical position), but that motion does not continue indefinitely and will eventually be counteracted.

References

Indian inventions Perpetual motion {{physics-stub