Too soon for cinchona to reach Europe?
If the Romans embraced some ship designs used by some Gauls/Britons which were more or less proto Cogs.
Could also have copied compartmentalization from the Ancient Chinese...
I seem to recall there were disinfectant poultices used in Roman times, rejected in the Middle Ages. Had they just stayed in use...
And am I wrong the triangluar (lateen?) sail is an advance over the square sail? Developing full rigging would be a big jump. Even the block & tackle (already in place?).
I'm also going to suggest you take Ben Braddock's advice: plastic. The technology/chemistry to develop a variety of polymer existed in Ancient Egypt.
(
Believe it, or stuff it.
)
Maybe make explosives with clay or ceramic...?
Yeah, metallurgy for long guns or cannon is problematic. (Bell-maker might be able to produce cannon.) Better advice: use a mangonel or something to throw ceramic jars full of lit gunpowder.
Might use a similar idea to create land mines. (IDK if you could produce pressure triggers. Flintlock "foot pedals"? Or discover fulminate of mercury?)
earlier discovery of the toxicity of lead could have far-reaching consequences.
The Romans understood lead was toxic. For reasons IDK, they did nothing about it.
There's also a bunch of food crops available in the Americas that never gained popularity, all of which could seriously affect the European diet (& ag output); I recall an entire issue of
The Plain Truth dedicated to it. (It's the only one I've ever actually kept.
)
And how about making the vertical-axis windmill the standard? It's way more efficient.
a pain in the [Insert random anatomical part].
Nikta.