Oscar Reutersvärd (2021) (escherinhetpaleis.nl)

The Escher in The Palace site profiles Swedish artist and art historian Oscar Reutersvärd, who created iconic “impossible” drawings such as the impossible triangle and staircase years before they were published by the Penrose mathematicians. It notes that Reutersvärd developed these figures consistently using isometric perspective, pursued them as a lifelong obsession, and was later re-discovered through events like Swedish Post stamps and books that helped renew interest in his work.