Reference for Eruvin 152:3

ה"מ עיגולא דנפיק מגו ריבועא אבל ריבועא דנפיק מגו עיגולא בעינן טפי מ"ט משום מורשא דקרנתא

- This<span class="x" onmousemove="('comment',' That the perimeter of a square exceeds the circumference of a circle by one quarter.');">⁶</span> applies only to a circle that is inscribed within<span class="x" onmousemove="('comment',' Lit., 'that goes out from'.');">⁷</span> the square, but where a square is to be inscribed within a circle it is necessar [for the circumference of the latter] to be much bigger.<span class="x" onmousemove="('comment',' Than three quarters of the given square. Hence R. Johanan's requirement that the circumference of the window must be no less than twenty-four handbreadths.');">⁸</span>

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