> The average normal temperature of the healthy human body in its interior, or in carefully covered situations on its surface, varies, according to the plan of measurement from 98.6° to 99.5° Fahr. (37° to 37.5° C.). It is about 98.6° in the well-closed axilla, and a few tenths of a degree higher (.5-1½ or 2° Fahr., .7° Fahr. average) in the rectum and vagina.
So, as far as I can tell it's not a sig-figs issue in conversion, but the actual original source that produced "98.6°". It almost seems like Wunderlich should've used 37.0° to 37.5°C to be consistent.