Do you have a link for that article?
I tend to collect pdf's concerning Time of Death, and causes.
There is a good one that describes what 19th century doctors used to help determine ToD - Algor mortis, Livor mortis, Rigor mortis, Decomposition, etc., plus Niderkorn's tables which were the standard for the time.
What I have not been able to locate is a 19th century source which explains how Rigor mortise develops. I'm sure they were not aware it was due to chemical reaction.
I would like to know if they thought it was the result of temperature, but I just don't know.