A Book within a Book

In The Fingerprint of Jack, Mrs. Steers has a very interesting book.  In fact, it's the one she used to learn how to time-travel.  
I have designed the book cover and it will be used somewhere in the book.  The name was inspired by 19th century book titles that explained what you would be reading in it.   I discovered the image in a book of pre-copyright materials and just loved it.   The hour glass with wings is a perfect symbol.
Too bad this book doesn't exist in our world.