This mysterious carving behind the office’s desk is a 15×15 grid of 225 numbers. It was carved in 1887, one year prior to Carlton’s death.

The entire grid is 7.5 feet by 7.5 feet, and each cell is 6 inches by 6 inches. The numbers range from 1 to 9,999. No two numbers are alike. There are no apparent patterns. And there is nothing in Carlton’s vast writings that reference the grid.

Cryptanalysts, numerologists, and mathematicians from all over the world have studied these numbers, yet none have been successful in unlocking the meaning behind them.

Although the numbers appear to be random, the general consensus among the experts is the grid is some type of cipher, since Carlton was, among other things, fascinated by cryptology and numerology. However, that was where agreement ended and hotly contested debates began.

In the end, to this day, the number grid remains a mystery.