“An art which cannot be specific in detail cannot be transmitted by prescription, since no prescription for it exists… This restricts the range of diffusion to that of personal contact”.
Cited in Polanyi’s Social Construction of Personal Knowledge and the Theories of Situated Learning. Frade, Cristina. UFMG. http://people.exeter.ac.uk/PErnest/pome17/pdf/polanyi.pdf