L. Frank Baum,
The Tin Woodman of Oz — Chapter 19…
(1918)
“ We can see the grass, and the flowers, and the stretch of plain before us, and we can still see Mount Munch in the distance; but we cannot see ourselves or one another.""Well, what are we to do about it?" demanded Woot."I think this magic affects only a small part of the plain," replied Polychrome; "perhaps there is only a streak of the country where an enchantment makes people become invisible. ”
