Mowing with child on your lap

Several year ago while mowing I noticed a slight noise and cought a glimpse of something flying from my mower and striking the side of my house.. After further inspection noticed that is was about half of one of the sides of the drive pulley and it was buried several inches into the cedar siding.. Not a doubt in my mind it would have cut a kids leg off or killed them if it struck their neck or head.. Now I always make sure kids are inside...