Chris, nice engraving with bows and staff slings throwing grenades!
Johnny,
you are finding many things in the historical texts!!
The caltrops thrown by sling have been used initially by the Romans, and afterwards in Middle age by English, Italian, Spanish and others. This subjet is and old discussion in wich myself, Dan Bollinger and others were involved. The problem was to find the sort of sling that can throw the caltrops, as a conventional sling entangle the cords in the caltrop pikes. I posted then a drawing of Leonardo Davinci showing some sling designes that included, maybe, a sling to throw caltrops, but the drawing was deficiency and the discussion about it did not clarify the question, as the caltrop depicted may be in connection with the sling or with the device in the botton of the drawing, been the overlapping with the sling just a coincidence.
May be in this forum someone can find a full and better copy of the Davinci drawing.
It´s interesting too in the Davinci drawing that splited shaft wit a stone between, a sort of staff sling that release the stone when you turn the wrist in the throwing.