The book Einleitung zur Berechnung der Leibrenten und Anwartschaften, published in Leipzig in 1785 (first part) and 1786 (second part) was a landmark of actuarial science. It contains an extensive synthesis of previous work on the subject, from Halley's mortality table to Richard Price's Observations on reversionary payments. It is recognized by actuaries for featuring the first risk measure ever (the Risico der Casse);[6] moreover it offers some insights in mathematical statistics: by using an approximation of the binomial distribution, Tetens tried to compute the confidence level of a given sampling procedure.[7]