Responsa for Bava Metzia 210:1

עלו באילן שכוחו רע ובסוכה שכוחה רע טמא

If they ascended a tree of feeble strength, or a feeble branch, he is unclean.<span class="x" onmousemove="('comment',' Zab. III, 1. This refers to a person who suffers from issue and a clean person. Now, if the two sit on an object in such a manner that one causes the other to move, e.g., on the two ends of a see-saw, on a rickety branch, whether the unclean person supports the weight of the clean person or vice versa, even if they do not come into actual contact, the clean person is defiled. Now, when they both ascend a feeble tree, which bends under their weight, or a feeble branch, even if the tree itself is strong. the same result ensues, one bending over — technically called 'leaning' — through the other, hence the clean person is defiled. ');">¹</span>

Teshuvot Maharam