Liturgy for Niddah 122:21

מתני' היא דתנן בודק עד שמגיע לסלע ואי ליכא אימר עורב נטלה

it is then permitted to be worn.<span class="x" onmousemove="('comment',' The assumption being that the threads of the other kind have somehow dropped out of the texture. ');">¹⁸</span>

Seder Ma'amadot