shall see Trees, Animals, Hunters Faces, and all the rest so plainly, that they cannot tell whether they be true or delusions: Swords drawn will glister in at the hole, that they will make people almost afraid." Della Porta claimed to have shown such spectacles often to his friends. They admired it very much and could hardly be convinced by Della Porta's explanations that what they had seen was really an optical trick. 1600 to 1650: Name coined, camera obscura telescopy, portable drawing aid in tents and boxes The earliest use of the term "camera obscura" is found in the 1604 book Ad Vitellionem Paralipomena by German mathematician, astronomer, and astrologer Johannes Kepler. Kepler discovered the working of the camera obscura by recreating its principle with a book replacing a shining body and sending threads from its edges through a many-cornered aperture in a table onto the floor where the threads recreated the shape of the book. He also realized that images are "painted" inverted and reversed on the retina of the eye and figured that this is somehow corrected by the brain. In 1607, Kepler studied the sun in his camera obscura and noticed a sunspot, but he thought it was Mercury transiting the sun. In his 1611 book Dioptrice, Kepler described how the projected image of the camera obscura can be improved and reverted with a lens. It is believed he later used a telescope with three lenses to revert the image in the camera obscura. In 1611, Frisian/German astronomers David and Johannes Fabricius (father and son) studied sunspots with a camera obscura, after realizing looking at the sun directly with the telescope could damage their eyes. They are thought to have combined the telescope and the camera obscura into camera obscura telescopy. In 1612, Italian mathematician Benedetto Castelli wrote to his mentor, the Italian astronomer, physicist, engineer, philosopher, and mathematician Galileo Galilei about projecting images of the sun through a telescope (invented in 1608) to study the recently discovered sunspots. Galilei wrote about Castelli's technique to the German Jesuit priest, physicist, and astronomer Christoph Scheiner. From 1612 to at least 1630, Christoph Scheiner would keep on studying sunspots and constructing new telescopic solar-projection systems. He called these "Heliotropii Telioscopici", later contracted to helioscope. For his helioscope studies, Scheiner built a box around the viewing/projecting end of the telescope, which can be seen as the oldest known version