משנה אויף תהילים 1:3

One whom Gentiles, or an evil spirit, have taken out [beyond the Shabbat border] has no more than four cubits [in which to move]. If they brought him back, it is as if he had never gone out. If they took him to another town, or if they put him in a pen or a sahar: Rabban Gamaliel and Rabbi Elazar ben Azariah say he may move throughout the entire area; But Rabbi Joshua and Rabbi Akiva says: he has only four cubits [in which to move]. It once happened that they were coming from Brindisi and their ship sailed out to sea [on Shabbat]. Rabban Gamaliel and Rabbi Elazar ben Azariah walked about throughout its area, but Rabbi Joshua and Rabbi Akiba did not move beyond four cubits because they wanted to be stringent upon themselves.