The chronophone is a weird device with weird limitations suited to the purposes of EY in that post.
This is a much more straightforward question (but note the context -- it asks where should that person put his money, not what kind of tech he should invent).
In particular, there is an interesting implication/sub-question: what was the cheapest way of saving the most lives in 1400 and do you think that was the best use of resources?
it asks where should that person put his money, not what kind of tech he should invent
A nontrivial chunk of EA is allocating money to tech invention, though, especially if you consider institutions and institutional design to be social tech.
Open borders advocacy, for example, would probably translate to infrastructure investments in the 1400s. (Build more lighthouses, map out channels, build and guard more roads, set up mail links, etc.)
But yeah, GiveDirectly would have an obvious analog in 1400. And SCI, if you were able to somehow transmit the 'pathog...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.