What kind of book ("folio volume") was in the middle of Dr. Heidegger's study in "Dr. Heidegger’s Experiment"?

In "Dr. Heidegger's Experiment," the rather eccentric Dr.
Heidegger has invited four of his old (and miserable) friends to his study, a "curious
place." It's full of many things, including volumes and volumes of books.  The folio to
which you refer is seen in the middle of the table and it draws everyone's attention
even in the midst of so many other books.  Hawthorne describes it this
way:

The
greatest curiosity of the study remains to be mentioned; it was a ponderous folio
volume, bound in black leather, with massive silver clasps. There were no letters on the
back, and nobody could tell the title of the
book.

That's what it looks
like.  More importantly, though, this particular book has special properties which will
be pivotal to the experiment to come.

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But it was well known to be a book of magic; and
once, when a chambermaid had lifted it, merely to brush away the dust, the skeleton had
rattled in its closet

and
other static elements in the room came to life.  This is a book of magic, then, from
which Dr. Heidegger does his magical work.