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.

[–] sylver_dragon@lemmy.world 5 points 1 month ago

Cauterizing wounds is still used in some cases.
Source: I had it done on a finger tip I sliced a chunk off of. The difference is that doctors generally use Silver Nitrate and then slather it with betadine to prevent infection. Hurts like a motherfucker, do not recommend.