The Aboriginal languages of southeast Australia have an ingenious counting system – there’s a physical mnemonic built directly into the language.
The Wurundjeri counting system is named after parts of the body. Beginning with the pinky finger (giti mŭnya), the numbers work their way across the fingers to the thumb, then the wrist, forearm, elbow, bicep, shoulder… eventually ending up at the crown of the head (det det), which is the number fifteen.
Those examples are from the Wurundjeri, but a similar counting system must have been spread across nearby peoples, because the system was used to communicate between them. Message sticks were inscribed with numbers and sent with a messenger to plan shared events like corroborees.