The statement was obtained “from two highly respectable clergymen, the Rev. Mr. Austin and the Rev. A. Ely, D.D., residing in Monson, Mass”.
http://solomonspalding.com/docs1/1842ClkB.htm#pg216a
In the Boston Recorder (April 8, 1839), John Storrs reported:
“Having heard incidentally that there was a lady in Monson, Ma., whose husband now dead was the author of the book, I requested in a note, Rev. D. R. Austin, Principal of Monson Academy, to obtain of her, for my benefit, and to be used as I should think proper, a certified account of its origin with her husband; for the character of which lady I wished the venerable Dr. Ely and himself to avouch. The following highly satisfactory document came in reply.”
http://sidneyrigdon.com/dbroadhu/NE/miscne01.htm#041939
In Gleanings by the Way, Storrs explained to John Clark that Matilda did not write the statement:
“I requested in a note, Rev. D. R. Austin, Principal of Monson Academy, to obtain of her, for my benefit, and to be used as I should think proper, a certified account of its origin with her husband.”