Reference for Shabbat 85:12

ת"ש פורסין מחצלות על גבי אבנים בשבת באבנים מקורזלות דחזיין לבית הכסא

at twilight, it remains so forbidden for the whole day.<span class="x" onmousemove="('comment',' This is a principle often met with. But if the basket is placed there after nightfall, so that it was fit for handling at twilight, it may be moved when the birds are not upon it. ');">¹¹</span>

Jastrow