Übersetzung - Englisch-Spanisch - If you don't care what others think...

I checked the story, thanks for making me gain this piece of knowledge. It is really amazing how sharp the irony is since the situation is quite common.
The story says that Su Dongpo was quite sure that his mind is so much at peace that none of what others think would influence it, so he wrote 八风吹不动，端坐紫金台, expressing this idea to his buddist friend. The friend frankly told him to "f-off", and Su Dongpo was enraged and rushed to the other side of the river to ask what was wrong with the statement, thus showing that his mind was, in fact, not totally free from the opinion of others. His friend pratically satirized him by saying 八风吹不动，一屁过江来: well, didn't you say that you wouldn't care what others think?
The translation can't really be done word for word because 1.it is some fragment of a poem, 2.it will be hard to explain in a few words what the "eight winds" means, and this is the best I can do.
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(Ian's notes)
Here is a more literal translation:
You claimed to not be moved by the winds from the eight directions,
but my little fart blew you clear across the river!

Here is Pluiepoco's interpretive translation, of the meaning of the friend's comment:
One is moved only by the desires within oneself.