During a bog standard CatIII approach, (a regular feature in Europe for several months of the year), the PF will have one hand on the control yoke, guarding the auto-pilot dis-connect button, and one hand on the throttles guarding the auto-throttle disconnect/ TOGA switch, in the event that at any time any indications shouldl move outside the accepted parameters for an autoland under CatIII conditions, then the PF will take immediate control of the aircraft and carry out a go-around/over shoot. On the B747-400 this situation could occur at a height of 20' agl and no visual reference outside the aircraft.
Under such circumstances having ones hands on ones knees is not recommended, but if in doubt, try it out!