The first link describing the difference between a one foot and two foot crossbow is partially false. There was never a time one when one placed one foot on the lath and then spanned the arbalest. Laths and bows both have to be carefully tillered so that both limbs pull the same or they're inaccurate. stepping on just one limb or even in the center would tend to throw them out of tiller.
The difference between the two types is that the lighter "two foot crossbows" (AKA arbaltetes a deux pieds) was spanned with both feet stepping on the lath and ones hands spanning the arbalest, while the one foot arbalest (AKA arbalest a ettrif) had a stirrup that one placed a foot in and the crossbowman spanned it with a girdle worn around his waist with a claw suspended from it that was hooked on the string and he spanned it by handing the butt of the tiller and standing up.
The arbalest a tour was also not the springald. There's a difference between the way a modern crossbow and a medieval or ancient European were held. The traditional "crossbow" was held more like a bow, that is with the lath almost vertical rather than the later horizontal method. When was shooting from inside a tower or from and arrow loop in a merlon it was highly desirable for the lath to be as absolutely vertical as possible to so a top-tiller was added to keep the quarrels from falling off the tiller, this allowed the crossbowman a greater up and down positioning of the lath while shooting and also allowed him to not to expose any of his body to an extremely lucky shot through the arrow slit he was shooting from. Likewise the horizontal slits one sees in some arrow loops were not for "crossbows", but were actually slights for either a bowman or arbalester to use to better see.
Some useful illustrations
http://picasaweb.google.com/11612624...66701183790530
http://picasaweb.google.com/11612624...66702517977874
http://picasaweb.google.com/11612624...69578950262338