During a short window, a samurai could’ve faxed president Lincoln (though I believe the samurai and Lincoln would have had to be in the same country)

You should look into how it was done. Weirdly enough, it’s pretty similar to how we lay cable now.

I remembered this article if you’re interested in how we lay cable underwater today. It’s even more wild since it’s fiberoptic cable. https://www.theverge.com/c/24070570/internet-cables-undersea-deep-repair-ships