Archimedes' heat ray

Archimedes is said to have invented a large scale solar furnace, sometimes described as a heat ray, and to have used it to burn attacking Roman ships during the siege of Syracuse. The device does not appear in Archimedes' surviving works and no contemporary evidence for it exists, leading modern scholars to doubt it was ever built. The story was already established by around 500 AD, when Anthemius described a reconstruction of it, and it has remained a subject of speculation about its plausibility ever since.