On October 22, 1938, xerography was demonstrated by Chester F. Carlson. With his assistant, Otto Kornei, Carlson used a sulphur coating on a zinc plate, vigorously rubbed with a handkerchief to apply an electrostatic charge. A glass slide was prepared using India ink to write "10-22-38 ASTORIA," then laid on the sulphur surface in a darkened room. After illuminating them with a bright incandescent lamp for a few seconds, the slide was removed. When lycopodium powder was sprinkled on the sulphur surface and blown off, there remained a near-perfect image of the writing. Permanent copies were made by transferring the powder images to wax paper and heating the sheets to melt the wax. Xerox is a term coming from "xerography" which means dry writing and is a trademark.
Source: TODAYINSCI: https://www.todayinsci.com/10/10_22.htm#event