Fragments of Theognostus of Alexandria

The substance of the Son is not a substance devised extraneously, nor is it one introduced out of nothing; but it was born of the substance of the Father, as the reflection of light or as the steam of water. For the reflection is not the sun itself, and the steam is not the water itself, nor yet again is it anything alien; neither is He Himself the Father, nor is He alien, but He is an emanation from the substance of the Father, this substance of the Father suffering the while no partition. For as the sun remains the same and suffers no diminution from the rays that are poured out by it, so neither did the substance of the Father undergo any change in having the Son as an image of itself.