This "remark" was made by a Gentleman called Stephen Graham, in his book "The Gentle Art Of Tramping" (1923);
"As you sit on the hillside, or lie prone under the trees of the forest, or sprawl wet - legged by a mountain stream, the great door, that does not look like a door, opens"
It does indeed.
(I came upon this in "The Wild Places" by Robert MacFarlane. A book I really enjoyed.)