1. Now, it comes forth clear to my reviewing a double definition, by Vi­tru­vi­us himself, which distinguishes the feet's posture for the circle from that of the square. While the first represents the spiritual zone, say where the body has no weight, the second the phisical one, where the man places his feet on the ground.

Hence, we must point out the exact outline: “face up­ward – lying on his back – with the hands and feet ex­tend­ed”.

[§3] Item corporis centrum me­di­um naturaliter est um­bi­li­cus.
    Namque si homo con­loca­tus fu­e­rit supinus mani­bus et pedi­bus pansis cir­cinique con­lo­can­tum cen­trum in umbilico e­ius, cir­cum­agen­do ro­tun­da­tio­nem utrar­um­que man­uum et pe­dum di­gi­­ti li­nea tan­gen­tur.
    Non minus que­mad­modum sche­ma ro­tun­da­tio­nis in cor­po­re efficitur, item quad­rata des­ig­na­tio in eo in­ve­nietur.
Nam si a ped­ib­us imis ad sum­mum caput men­sum erit eaque mens­ura rel­a­ta fuerit ad ma­nus pan­sas, in­ve­nietur e­a­dem la­ti­tu­do uti altitudo, que­mad­mo­dum ar­e­ae quae ad nor­mam sunt qua­dratae.
But how are hands and feet to be extended? only with arms in­side a square? dealing with a whole circle plot, this looks like an am­big­u­ous, contradictory definition.