Whitecold wrote:The problem with that is someone will notice the mercury being a different levels during day and night/winter and summer. Rather have the archangels make the invention already rather than having it been made afterwards.
How is that a problem? The people using it would KNOW it's being used to measure temperature. There just wouldn't be any official scale to measure temperature with and the lack of standardization in pre-Merlin Safehold means every thermometer would be slightly different.
And getting standard figures like what temperature water boils/freezes at is going to be difficult if you don't know in advance that things like air pressure and contaminants (salt for example) can change what temperature water boils/freezes at.