

Source: McClure's Magazine, June, 1899, pages 99-112:
MARCONI'S WIRELESS TELEGRAPH - MESSAGES SENT AT WILL THROUGH SPACE.--TELEGRAPHING WITHOUT WIRES ACROSS THE ENGLISH CHANNEL.
BY CLEVELAND MOFFETT.
I love the description of messages traveling "THROUGH SPACE". Also do note the Spark Coil is clearly visible in the latter sketch.