That's the Unitarians. Newton's beliefs were personal and were unitarian in nature. That is, he firmly rejected the doctrine of the Trinity, based on his historical study of the Arian heresy.
Cf. Westfall, The Life of Isaac Newton, under Arianism in the index. "The mere thought of trinitarianism, the 'fals infernal religion,' was enough to fan Newton into a rage." And Newton blamed it for what he saw as the degraded practice of Christianity, represented chiefly by Roman Catholicism, but not excepting Anglicanism.
Newton came near to sacrificing his academic career for his beliefs, as he was prepared to refuse ordination into the Anglican Church, which had been a requirement for his position at Cambridge, and would have involved swearing to beliefs abhorrent to him. Fortunately, we may say, some adroit politicing voided this requirement in the nick of time.
The Unitarians (as opposed as to unitarians) seem to have three beliefs, The Fatherhood Of God, The Brotherhood Of Man, and The Neighborhood Of Boston.