Henry S. Whitehead, The trap (1932)
“ That looking-glass had indeed possessed a malign, abnormal suction; and the struggling speaker in my dream made clear the extent to which it violated all the known precedents of human experience and all the age-old laws of our three sane dimensions. It was more than a mirror—it was a gate; a trap; a link with spatial recesses not meant for the denizens of our visible universe, and realizable only in terms of the most intricate non-Euclidean mathematics. And in some outrageous fashion Robert Grandison had passed out of our ken into the glass and was there immured, waiting for release. ”
