Formula to change into a cat:

I shal goe intill ane catt,
With sorrow, and sych, and a blak shott;
And I sall goe in the Divellis name,
Ay quhill I com hom againe.

To return to human form:

Catt, catt, God send thee a blak shott.
I am in a cattis liknes just now,
Bot I sal be in a womanis liknes ewin now.
Catt, catt, God send thee a blak shott.