A Journal of Impossible Things (Human Nature)

The Journal of Impossible Things was a journal kept by John Smith of his strange dreams - actually memories from his life as the Doctor's tenth incarnation, with some memories of previous incarnations' appearances. All but Martha Jones believed these to be products of John Smith's imagination.

With John Smith
After turning himself human to hide from the Family of Blood, John Smith began to experience dreams of his adventures as the Doctor.

After John Smith
John Smith gave the book to Joan Redfern, who apparently annotated it with a detailed chronicle of her love story with a strange visitor from beyond the stars. In the 21st century, this annotated version of the book fell in possession of her great grand daughter, Verity Newman, who published it, again titled Journal of Impossible Things, as a partial biography of Joan herself. The Doctor, slowly dying from radiation sickness, attended a book signing by Newman, giving away his identity by naming himself as "The Doctor". He then asked Verity about Joan, going away to meet his final fate after being assured of Joan's ultimate happiness in life. (DW: The End of Time)

He then kept the book in his TARDIS's drawing room. (VG: TARDIS)

Illustrations
Among the many illustrations Smith made in his journal were:
 * The TARDIS
 * The TARDIS Console
 * Steaming TARDIS Console
 * Sonic screwdrivers
 * TARDIS Crystal
 * New Gallifreyan words
 * Torchwood Institute logo
 * Empty People
 * Gas Mask
 * Dalek Top
 * Dalek Saucer
 * Dalek
 * Cybermen
 * Cyberman Faceplate
 * Vortex Reapers
 * The Doctor's first nine incarnations
 * Rose Tyler
 * Family of Blood
 * Fob Watch
 * The Moxx of Balhoon
 * Wired-People
 * Autons
 * Raxacoricofallapatorian
 * Big Ben
 * Raxacoricofallapatorian Inter-Stellar Transporter
 * References to the Doctor's family
 * Mighty Jagrafess of the Holy Hadrojassic Maxarodenfoe
 * Satellite Five (The Game Station)
 * Cat Nurses
 * Lupine-Wavelength-Haemovariform
 * K9
 * Clockwork Droid
 * Martha Jones
 * Joan Redfern
 * Dalek Emperor
 * Anne Droid
 * Captain Jack Harkness
 * Pilot fish
 * Fadros Pallujikaa
 * London Eye
 * London Eye Capsule
 * Rose's face on television set
 * Ood
 * The Beast
 * Toby Zed
 * Tenth Doctor
 * Nottingham?
 * Empire State Building
 * William Shakespeare

Behind the scenes

 * An actual, intricately-illustrated prop book was created for the filming. Later, Character Options, which held some of the rights to release toys and merchandise based upon the series, issued a faux leather-bound reproduction of the book. The CO journal it is not as big as the one in the episode.
 * The images of the Doctor appearing in the journal were taken from a collage of past incarnations used as the illustration for the Wikipedia article on the Doctor, though they were inverted.