This is just an unroganized set of old drawings of penumbra showing filaments. If no link is provided then I forgot the source of the image. I have been trying to figure out which is the oldest reference pointing out that penumbrae have filaments.
The beatifull Galileo's Sunspot Drawings are not included here because I have not been able to distinguish penumbral filaments
J. H. Schroeter.
Drawing bewteen 1785 and 1795. The penumbral filaments are evident
John Hershel (1837)
One can read 'best glimpses striated appearance of penumbra'
