In the seventh edition of a work on gardening and planting, published
in 1739, by Richard Bradley, F.R.S., late Professor of Botany in the
University of Cambridge, we find the following details of an invention,
“by which the best designers and draughtsmen may improve and help
their fancies. They must choose two pieces of looking-glass of equal
bigness, of the figure of a long square. These must be covered on
the back with paper or silk, to prevent rubbing off the silver. This
covering must be so put on that nothing of it appears about the edges
of the bright side. The glasses being thus prepared, must be laid face
to face, and hinged together so that they may be made to open and shut
at pleasure like the leaves of a book.” After showing how various
figures are to be looked at in these glasses under the same opening,
and how the same figure may be varied under the different openings, the
ingenious artist thus concludes: “If it should happen that the reader
has any number of plans for parterres or wildernesses by him, he may by
this method alter them at his pleasure, and produce such innumerable
varieties as it is not possible the most able designer could ever have
contrived.”