This puzzle is part of the historic Canterbury Puzzles by Henry Ernest Dudeney. Puzzle of the Prioress
The Prioress, who went by the name of Eglantine described the puzzle: "A learned man from Normandy did once give me this brooch as a charm, saying strange and mystic things anent it, how that it hath an affinity for the square, and such other wise words that were too subtle for me." But the good Abbot of Chertsey did once tell me that the cross may be so cunningly cut into four pieces that they will join and make a perfect square; though on my faith I know not the manner of doing it."
Peter was also known as Simon Peter or Simeon. Saint Peter, according to the New Testament, was an early leader of the Christian Church and one of the Twelve Apostles of Jesus Christ.
The curiously-shaped cross may be cut into four pieces that will fit together and form a perfect square. How this is done is shown in the illustration.
Cut this odd-shaped cross into four pieces to make it form into a perfect square. The origins of this interesting puzzle comes from an old publication entitled "The Project Gutenberg eBook of Amusements In Mathematics, by Henry Ernest Dudeney" and adapted it to my images.
The Heraldry shield displays in Medieval stained glass in the Chertsey Abby. The shield contains the arms of the abbey, a sword and the keys of St Peter. Color book version is located at Shields of Heraldy