No rack can torture me

No rack can torture me,
My soul's at liberty
Behind this mortal bone
There knits a bolder one

You cannot prick with saw,
Nor rend with scymitar.
Two bodies therefore be;
Bind one, and one will flee.

The eagle of his nest
No easier divest
And gain the sky,
Than mayest thou,

Except thyself may be
Thine enemy;
Captivity is consciousness,
So's liberty.