Library Eusebius of Caesarea Church History
Book 4, Chapter 28: Musanus and His Writings.
And as for Musanus, whom we have mentioned among the foregoing writers, a certain very elegant discourse is extant, which was written by him against some brethren that had gone over to the heresy of the so-called Encratites, which had recently sprung up, and which introduced a strange and pernicious error. It is said that Tatian was the author of this false doctrine.
English translation by Arthur Cushman McGiffert, in Nicene and Post-Nicene Fathers, Series II, Vol. I (eds. Philip Schaff and Henry Wace; Buffalo: Christian Literature Publishing Co., 1890). Public domain. Digital text via New Advent Church Fathers.