Rittenhouse was mentioned in Timothy Dwight's Triumph of Infidelity as one of those "infidels" who presented his system under the auspices of "Christianity" but in reality was too man centered/humanistic to qualify as "real Christianity."
But anyway here is a passage from an old book where Rittenhouse's widow describes his creed:
[D]ated August 20th 1797. "'That you were sufficiently authorized to assert what you did respecting Mr. Rittenhouse's religious principles, I now add my testimony to what you have said, for well I know the great truths of religion engaged much of his attention, and indeed were interwoven with almost every important concern of his life. I do not recollect, if in any of the conversations I have had with you, I informed you, what I now do, that Dr. Price's opinions respecting Christianity were more in unison with his own, than any others of the divines; that Dr. Price's sermons was the last book he requested me to read to him, and that the last morning of his life, he reminded me that I had not finished one of the Doctor's discourses , which I had began the proceeding evening."
The Dr. Price referred to is the Arian heretic, "rational Christian," Richard Price.