Reference for Eruvin 152:4

מכדי כל אמתא בריבוע אמתא ותרי חומשי באלכסונא בשיבסר נכי חומשא סגיא

What is the reason? In order [to allow<span class="x" onmousemove="('comment',' Within the circle.');">⁹</span> space for] the projections of the corners.<span class="x" onmousemove="('comment',' Of the square. A circular window with a circumference that is less than twenty-four handbreadths would not contain the area that is required.');">¹⁰</span>

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