Tech, your speech has been great

, I´ve had a lot of fun, and the information on Spanish old measures is extremely interesting, as to have it before one when reading old Spanish texts, as for example the Cronicas de la Conquista.
The quote of Johnny has been used frequently by different authors in all times and thus it has been deteriorated as it is logical, changing units and facts according to the exactitude and quality of the author. For that reason the observation of Jeff is not superfluous, and it´s always advisable to mention the author of quoted texts.
The original quote is from Alonso Enriquez de Guzman, who accompanied Pizarro and fought beside him at the siege of Cuzco. The ideal would be to transcribe the quote as he wrote it, in old Castilian, but unfortunately one has to translate it to modern English although it loses great part of its original taste. It says, more or less, talking about to the Incas of Manco Cápac:
"The main weapon they have is the sling, that uses it from childhood. When they are born they already wear it on the head like a cap. With it they throw very big stones that can kill a horse and sometimes to the rider although they strike to him in the helmet. Their slings are really almost as lethal as arquebuses. I have seen breaking in two pieces with the sling an old sword that a man had in the hands, to a distance of thirty
pasos".
So, in the first place, the quote was about the Incas of Peru. Secondly, it was an "old" sword , what it seems to indicate of smaller hardness and solidity. Third, it talks about thirty "pasos", that would correspond to about 20 meters aprox. But in any case the exact distance is not important here since the author is not speaking specially of accuracy with the sling, but of power when breaking the sword.
The slings of the Incas were without a doubt frightful, and at the same siege of Cuzco where the event of the sword takes place, a brother of Pizarro, Juan Pizarro, was struck by a stone of sling on the head, and since he had forgotten to wear the helmet, his skull was broken, dying fifteen days after.