Auguste Piccard was a Swiss-Belgian physicist, inventor, and explorer, known for his record-breaking balloon flights to the stratosphere, as well as the invention for bathyscaphe to allow for deep ocean exploration.
Unfortunately for him, flat-Earthers are claiming him as their own these days. It started from a Popular Science article from 1931, saying:
Through portholes, the observers saw the earth through copper-colored then bluish, haze. It seemed a flat disk with upturned edge.
But, no. In reality, Auguste Piccard was not even close to being a flat-Earther.