Reminds me of a reference in another of Lewis’ books, “The Great Divorce”, where the visitors to Heaven that had come on a bus for a visit from Hell. The visitors were screaming in pain as the grass was injuring their bare feet. They were too insubstantial to bend the grass. Therefore, the grass was like walking on nails.
Another Lewis reference I’ve always liked from “The Last Battle” describes the inside of something as being larger than the outside. I like that a lot.
“The Great Divorce” is one I definitely need to read.