Here is an excerpt from his book, The Zen of Seeing, written in 1973.
"Zazen (sitting in meditation) may be the discipline of Zen, but I, for one, am not good at sitting still for long in the lotus position. I believe that in SEEING/DRAWING there is a way of awakening the "third eye," of focusing attention until it turns into contemplation, and from there to the inexpressible fullness, where the split between the seer and what is seen is obliterated. Eye, heart, hand become one with what is seen and drawn, things are seen as they are - in their "isness." Seeing things thus, I know who I am!!!
May it be so!