Runed Lexicon

The Dragonborn receive a Blank Lexicon by Septimus Signus. After filling it during the quest Discerning the Transmundane it becomes a Runed Lexicon, won't disappear after the quest is complete, and cannot be removed from inventory since it is a quest item, leaving it struck in the inventory (unlike the "Elder Scroll" which can be sold to Urag gro-Shub).

PC players can type "player.removeitem 0003a3dd 1" to get rid of it.