Tres epistolae de macvlis solaribvs : scriptae ad Marcvm Velservm ... Cum obseruationum iconismis
Three Latin letters on sunspots addressed by the Jesuit astronomer Christoph Scheiner to the Augsburg scholar Marcus Welser, printed at Augsburg in 1612 for mathematicians and natural philosophers. The plates are line-engraved observational diagrams: a large circle standing for the solar disc, small dark spot-forms lettered for reference, converging sight-lines running down to an observer with a telescope, and captions set inside the figure.
