You remember calculus, right? In a time before mechanized computing was performed by computers, complex (or sometimes just clever) machines were used to automate calculations. One example that has always impressed and fascinated me is the wheel-and-disk integrator, a simple machine capable of solving the calculus equations you labored over in high school without breaking a sweat. While this concept was used most impressively in Vannevar Bush's differential analyzer, an analog computer built in 1931, the chances are good that you've seen one in a more mundane application around your house: the power meter. Click on the photo gallery to see inside one and how it works, and follow the jump for more in-depth electro-geekery.