In that he states
"Newton was an MP for almost exactly one year, but he seems to have contributed nothing personally to the proceedings of the new parliament. He reported back to the Vice-Chancellor faithfully and in minute detail, but according to one anecdote, which may or may not be true, he said only one thing during the year-long proceedings. Feeling a draught down his back, he asked a nearby usher to close an open window."
But there is no other reference in that book to where that came from.
Official records of what was and what as not said in Parliament didn't really come into the public until Hansard (circa 1800) there is 'WIlliam COBBETT's parliamentary history of England : from the Norman conquest, in 1066, to the year, 1803' which has been a reference before the 1800's and you can find a copy of that on the Internet Archive
https://archive.org/details/pp809777_0001/mode/2up
There is one reference to the string 'Newton' in that search but it is just a name of a borough.