These were the documents that spurred my "happy dance" moment (described here).
My descent from William Backus(1) through Stephen Backus (there is another line through Stephen's sister, Sarah):
William Backus m. ____
Stephen Backus m. Sarah Spencer
Timothy Backus m. Sarah Post
John Backus m. Joanna Cleveland
John Backus m. Jerusha Baker
John Backus m. 4 times
Laura Backus m. Thomas P. Richmond
The documents were found via the Family History Center microfilms (viewed at Jonesville, Michigan). The microfilm information used to order the Tompkins Co., NY Probate was also found here.
The following (on an Ancestry message board) is the last Will and of John from Will Book I 137-139 in the Tompkins Co., NY, Deeds.
Additional probate information (not included on the documents above) can be found here.