"Hawkins, 40, Palm's chief technologist and Pilot's creator, designed one of the first handheld computers, the GRiDPad, a decade ago. It was an engineering marvel but a market failure because, he says, it was still too big. Determined not to make the same mistake twice, he had a ready answer when his colleagues asked him how small their new device should be: "Let's try the shirt pocket."
Retreating to his garage, he cut a block of wood to fit his shirt pocket. Then he carried it around for months, pretending it was a computer. Was he free for lunch on Wednesday? Hawkins would haul out the block and tap on it as if he were checking his schedule. If he needed a phone number, he would pretend to look it up on the wood. Occasionally he would try out different design faces with various button configurations, using paper printouts glued to the block."
Prototyping.club/ Palm Pilot - Wood Prototype
Case studies in prototyping