The 47th Problem of Euclid is also called the 47th Proposition of Euclid or the Pythagorean Theorem. It appears to be a mainly English (origin) symbol in Freemasonry. It appears on the frontispiece of Anderson’s Constitutions of 1723 and can often be seen on tracing boards. The symbol constitutes basic geometry. Euclid is referred to in various Old Charges, Pythagoras less so, so that may be why “Euclid” is mentioned more often in Freemasonry. Even though nowadays this is mostly the symbol of a “Past Master” (somebody who has been Worshipful Master of a lodge), the usage in older times seems to indicate another meaning. Sometimes it can be seen on a Master’s board.
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