Martinus Crusius (1526-1607), one of the 16th century's German humanists, kept personal notes in diary form for the period 1596-1605. This academic professor has provided us in his Diarium (Diary) with a systematic collection of daily records of various personal, historic and literary notes. But he was also interested in recording the day-to-day weather, extreme weather events and other environmental phenomena, such as phenological events, vine-harvest dates etc. Over 3,000 descriptive daily records of weather and other environmental phenomena have been derived from the Diarium. Assessment of the data is attempted considering various historic and philological parameters relevant to the author, his time, his work and the Diary he kept. Data on snow and snow-cover are discussed in this paper. Crusius' terminology on snow is approached, and the numbers of days with snowfall and snow-cover for the period 1597-1605 in Tübingen (Germany) are compared with averages of the 20th century relevant meteorological data.