Sona is an oligosyntheic language designed by Kenneth Searight in the 1930s. It is described in his book Sona; an auxiliary neutral language (1935).
Although the book title indicates that it was an auxlang, Sona is actually quite difficult to classify. It has some characteristics of an engineered language (self-segregating morphemes within compound words and a limited number of morphemes). It contains a mixture of a priori and a posteriori words. To a small degree it is a philosophical language with words of related meanings often having similar sounds.