Digital images of manuscripts stored in the Galilean collection of the Central National Library of Florence are analyzed to obtain sunspot groups, their areas and heliographic positions. Overall, 142 drawings were processed. The way of drawing is usually schematic resulting in area uncertainty which may exceed a factor of two for small sunspots. We suggest that there is an upper limit of a factor of two between sunspot group numbers from the drawings and the actual ones. The computed penumbra-to-umbra ratio is consistent with modern observations. A distribution of sunspot latitudes versus time is reconstructed by means of two methods: exploiting the observation time noted by an observer and minimizing the day-to-day variability of sunspot latitudes.