On his way from Ascona to Essen-Mulheim via the Nufenenpass, the pilot used a Michelin road map on a 1 to 1 million scale. He was unable to convert the altitudes in Meters to feet. So he ended up too low and too slow in his overloaded Cessna 172 with 4 people on board and landed on a snow field. Subsequently the Cessna rolled over and was destroyed.