meaning of the phrase "silent health"?

Question

It is from Crash Course World History. It is at around 7 minute and 36 second. Here it goes:

"Though ten out of twelve had fallen, still the last two, as sure as death, were to be found on the first evening of rest over the bottle drinking a silent health to their dead companions.

Answer 1

To

drink to someone's health

is to toast someone and acknowledge them.

What the writer is saying is the remaining two were having silent (and sobering) drink in memory of the ten that had fallen.