The best shirt ever. It's only number 4 because the first three had science written so it was obvious to chunderheads what the shirts were about. Sydney Padua's awesome Lovelace & Babbage at 2D Goggles is my favorite intermittent reading. Especially all the notes that accompany the comic.
Do I need to spell it out. This is Ada Lovelace at work on the Difference Engine (some license taken - although the Analytical Engine was the more interesting one it never got built).
I would happily tattoo this picture on my body if the IP wasn't an issue. Sydney?