What is the one item Isabel secretly takes before leaving the Finch Farm?

Isabel
recognizes clearly the condition in which she lives.  She is to be moved from one setting of
enslavement to another.  Her own life and personal experience is moot in the face of the
institution of slavery, something that considers her an object that can be easily moved from
place to place.  She is forbidden to bring anything with her.  She wishes to do so, if nothing
else to validate her...