“Kim was the hero of the eponymous tale by Kipling. He was being trained for his secret service work on behalf of the British Raj — the Great Game. His training was conducted using stones on a tray. Now slides and video clips are used but essentially the training is the same. The advantages of Kim’s Game are that it is easy to conduct, it can be carried out in doors, and it is directly relevant to tracking in that it develops and sharpens both observational skills and, just as importantly, the memory.”
The SAS Guide to Tracking, page 53.