Use to do the same thing at my parents house with the maple tree in the back yard.
It always got me how the line would manage to wrap around itself near the branch instead of the weight pulling the line to the ground. If I could tie a knot that good that fast I would be happy. It got to the point there where a number of weights in the tree that would fall out of it without warning, usually while I was cutting the grass under it. And we will not talk about the half of a brick on a masons line that my father got hung up while trying to rig a 40 meter inverted vee.