While there has been considerable speculation about Nikola Tesla's claims that he developed an electric weapon, no proof exists and very few facts survive about the purported invention. The most notable fact about his "death beam" is that he once offered a prototype of the weapon to the Governor Clinton Hotel in Manhattan in lieu of payment for his bill. When the box was opened after his death, however, it was found to contain only common electrical components.
Tesla spoke of the potential of a electrical weapon on many occasions, and even claimed to have tested one, but no evidence or prototype was ever found. The weapon was based on electrostatic principles, generating a high voltage and using it to propel charged particles across a distance to strike a target. Tesla claimed the ray could be only used as a defensive weapon due to the large size of the construction and the generator necessary to power the device. Ultimately, the device was never built due to his inability to raise government funding for the project.
Tesla spent much of his life working with and studying energetic rays. Early in his career as an inventor, he experimented with x-rays, developing devices that could shoot beams up to 40 feet away and retain the energy to produce images. He also developed a lamp in 1918 that utilized many of the scientific techniques that would later be used to create laser beams.