Taking, first, dreams of the unknown past, we find a large modern
collection of these attributed to a lady named "Miss A---". They were
waking dreams representing obscure incidents of the past, and were
later corroborated by records in books, newspapers and manuscripts.
But as these books and papers existed, and were known to exist, before
the occurrence of the visions, it is obvious that the matter of the
visions _may_ have been derived from the books and so forth, or at
least, a sceptic will vastly prefer this explanation. What we need is
a dream or vision of the unknown past, corroborated by a document _not
known to exist_ at the time when the vision took place and was
recorded. Probably there is no such instance, but the following tale,
picturesque in itself, has a kind of shadow of the only satisfactory
sort of corroboration.

The author responsible for this yarn is Dr. Gregory, F.R.S., Professor
of Chemistry in the University of Edinburgh. After studying for many
years the real or alleged phenomena of what has been called mesmerism,
or electro-biology, or hypnotism, Dr. Gregory published in 1851 his
Letters to a Candid Inquirer on Animal Magnetism.

Though a F.R.S. and a Professor of Chemistry, the Doctor had no more
idea of what constitutes evidence than a baby. He actually mixed up
the Tyrone with the Lyttelton ghost story! His legend of Queen Mary's
jewels is derived from (1) the note-book, _or_ (2) a letter
containing, or professing to contain, extracts from the note-book, of
a Major Buckley, an Anglo-Indian officer. This gentleman used to
"magnetise" or hypnotise people, some of whom became clairvoyant, as
if possessed of eyes acting as "double-patent-million magnifiers,"
permeated by X rays.