Reference for Eruvin 116:8

רב הונא בריה דרב נתן מתני לקולא אמר רבא לא שנו אלא בהר המתלקט עשרה מתוך חמש אבל בהר המתלקט עשרה מתוך ד' אומדו והולך לו:

This<span class="x" onmousemove="('comment',' That the method of spanning or piercing is allowed.');">¹⁵</span> was learnt only in respect of a hill that has a rise often handbreadths to a gradient of five cubits,<span class="x" onmousemove="('comment',' Since it is not level ground one of the methods of spanning or piercing may be adopted.');">¹⁶</span> but a hill that has a rise of ten handbreadths to a gradient of four cubits<span class="x" onmousemove="('comment',' Being too steep and hardly suitable for walking.');">¹⁷</span>

Jastrow