I don't think any scientist ever contended that. People have known the earth was round for thousands of years. You might be thinking of Copernicus, and later Gallileo, who got in trouble for pointing out it the earth went round the sun and therefore wasn't the center of the universe.
Copernicus. In the 1500s Polish scientist Copernicus upset the standard belief of his time that the Sun and planets revolve around the Earth. He said the planets went around the Sun. The earth was known to be round as early as 7th century B.C. The answer to your question is unknown
Although Ferdinand Magellan's expedition was the first circumnavigation of the Earth, many ancient scholars were already aware that the Earth was round. The Greek scientist Eratosthenes was the first to calculate the Earth's circumference, thus proving the Earth's roundness.
A wise guy (literally), who noticed how ships that sail into ports always appear over the horizon, meaning that the earth is round, or else the ships would have travelled vertically on the "edge of the earth",