Related for Eruvin 195:6

תוך ד' אמות דאי נפיל ומייתי ליה לא אתי לידי חיוב חטאת שרו ליה רבנן

[Hence it is that if the end of the scroll rested] within four cubits where, even if [all the scroll] had fallen down a one would have carried it back,<span class="x" onmousemove="('comment',' To the threshold.');">¹³</span> no obligation of a sin-offering would be incurred,<span class="x" onmousemove="('comment',' Since the prohibition to carry from a public domain Into a karmelith is only a shebuth.');">¹⁴</span> the Rabbis have permitted the man to roll it back;<span class="x" onmousemove="('comment',' i.e., where an end is retained in the reader's hand, a shebuth to safeguard a shebuth was not considered necessary.');">¹⁵</span>

Kitzur Shulchan Arukh