Част 16 · Chapter 226

And the reason is that since the light of Yetzirah is drawn from the screen of ZA, which is VAK, therefore there cannot be in each one of Yetzirah more than the aspect of VAK. And this is what is meant by 'six Sefirot nest in Yetzirah.' For the greatest Partzuf of all of them is no more than VAK.