I was “handed the black spot” by the 7th Sea group, so all my research is in vain (unless I run my own 17th Century game, which might be interesting).
From the links below, I think the Descartes entry is the most interesting – not (only) for his philosophy (although the bit about the Pineal gland being the abode of the soul is fascinating), but also for his life and the people he ran across – plenty of stories to be found in the cracks.