The what! That’s so cool, thanks for sharing!

Pliny the Elder noted the use of glass vases filled with water to concentrate sunlight heat intensely enough to ignite clothing, as well as convex lenses that were used to cauterize wounds.

Ouch.

Cauterising wounds seems to have been a thing outside of movies. I'm not sure how effective it was. You removed the infectious agents but created a larger surface of attack.