I came across the expression libella maris in a scientific text from 19th century. There are many ways to parse it in the context, and one option that occurred to me is that maybe it stands for "sea level". After all, libella is where the word "level" comes from in the first place, although an analogy to another language is more probably French than English at that time. In the context of the text, certain measurements would be different at sea level than at higher altitudes.
Are there examples after, say, the year 1700 where libella maris stands for "sea level"? I am trying to judge whether that would actually be a valid interpretation, and the passage I saw is not quite decisive on its own. However, I emphasize that this question is inspired by that passage, not about it; I am generally interested in knowing whether this kind of reading is valid and whether I could use the phrase for "sea level" myself.
