Perron de la Jaiande
With this boulder, Meliadus (Meliodas), Tristan’s father, compared his strength with that of a giant.
When Meliadus was able to lift the stone, he crushed the giant with it. Tristan was the only other knight able to heft the Stone of the Giant. When Lancelot tried, he failed.
Source
Palamedes | c. 1240