One of the first drawings of a Tesla coil circuit, an illustration used by Nikola Tesla in his May 20, 1891 lecture "Experiments with Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination" before the American Institute of Electrical Engineers at Columbia College, New York. In this lecture he introduced the circuit as a means of generating high voltage, high frequency alternating current for a "wireless" lighting system. He patented the circuit April 25, 1891..