The ideal situation is that in which a trained linguistician devotes all his time and attention to describing his own language; he can then be his own source of information (or informant) and can, over the years, note down all the forms, all the types of utterances, of which he normally makes use, and then analyze, classify, and describe them completely. No one has ever wholly measured up to this ideal, and perhaps it is an ideal impossible of complete attainment; the closest that anyone has ever come to it was in the description which the Hindu grammarian Panini wrote of Sanskrit, the language of the Old Indian hymns of the Vedas.
Source: wiktionary