Iterating over a Binary Tree with O(1) Auxiliary Space

Question

Is it possible to iterate over a binary tree in O(1) auxiliary space (w/o using a stack, queue, etc.), or has this been proven impossible? If it is possible, how can it be

Answer 1

I think there's no way you could do this, as you should somehow find the nodes where you left off in a path and to identify that you always need O(height) space.