Nikola TESLA, “Apparatus for the Utilization of Radiant Energy”, US-Patent 685,957, issued on November 05, 1901 (Image courtesy of Reference 1)
On February 6, 1932 Tesla commented to the Editor of the NY Times that “You have given considerable space to the subject of cosmic rays, which seems to have aroused general attention to an unusual degree. Inasmuch as I discovered this wonderful phenomenon and investigated it long before others began their researches your readers may perhaps be interested in my own findings.”
Tesla’s original idea was published in a series of articles, published from 1896 to 1898, on Roentgen rays (eventually called X-Rays) and radioactivity in The Electrical Review.
His experiments in 1896 were greatly advanced through his invention of a new form of vacuum tube that could handle Megavolts. Tesla claimed that a radioactive body is simply a target that is continuously bombarded by small “bullets” projected from all parts of the universe. He was able to solve this mystery in 1899 with mathematical and experimental proof that the Sun and other heavenly bodies in the universe emitted great rays of energy in tiny particles animated by velocities faster than the speed of light (That was his comment---Einstein might disagree).
CERN had made some other comments on cosmic rays, but it looks like Tesla preceded their August 1912 comment .
Tesla commented that these rays had tremendous penetrative power that enabled them to traverse “thousands of miles” (We now know that it is far more than that) of solid matter without losing speed. While passing through space, he commented, filled with cosmic dust, they generate a secondary radiation of constant intensity that reached the Earth. His vacuum tube experiments bore his theory out.
He may not have been 100% correct in all of his hypotheses in this area, but his theory was pretty good for the late 19th century.
Reference 1: Nikola TESLA’s Radiations and the Cosmic Rays by Andre Waser, July 2000