@vesatimonen congratulations! How far off is the "not a square" non-solution and when was it discovered that it's not a square?

@hattom Henry Dudeney published his 5-piece solution in 1911 and at the same time pointed out that Sam Loyd's solution was faulty.
On this page there is a nice history (translate to english works):
https://mp.weixin.qq.com/s/Kb_oBJUdloy09loHT3cdqQ