Always interested to see what people take as evidence of being somewhere, or doing something (for me its sometimes this web site).
A number of the mountain huts on the routes up Mt Fuji offer a walking stick stamping service. Punters buy the stick at the bottom of the mountain and at each station it can be burnt/stamped with the route and the altitude of that hut.
The stick fulfills a number of functions – a mixture of practicality, a gradual sense of achievement as each stamp is added, proof of attaining the summit, and ends up as an artifact/souvenir.