Map from one of my digital creations: the Princess with the pea (version 2)
for the little story: "in a distant realm, a Prince is looking for a Princess with the finest qualities to marry her. He wanted to marry what he calls a "real Princess". Although he is presented with princesses, none of them find thanks to his eyes, for none seems to be a "real Princess".

A stormy night, a young woman drenched who says she is a Princess comes to the door of the castle to ask for hospitality. The Queen, determined to find a wife worthy of her son, welcomes her and makes her sleep on a pile of 20 mattresses and 20 Eider feather comforters, under which she has previously placed, purposely, a pea.

The next morning, when the Queen asked the Princess if she slept well, she replied that she had spent a dreadful night, embarrassed that she was by the presence of something so hard that her body was covered with hematomas. Such a sensitive skin can only be that of an authentic Princess. "
square card with envelope: size of card 12.5 cm x 12.5 cm (envelope provided).
Double a page where I can write the formula of your choice inside
the card itself has been printed on thick paper.