There is considerable import in creating more complete, better understood holdings of early meteorolog- ical data. Such data permit an improved understanding of climate variability and long-term changes. Early records are particularly incomplete in the tropics, with implications for estimates of global and regional temperature. There is also a relatively low level of scientific understanding of how these early measurements were made and, as a result, of their ho- mogeneity and comparability to more modern techniques and measurements. Herein we describe and analyse a newly rescued set of long-term, up to six-way parallel measure- ments undertaken over 1884–1903 in Mauritius, an island situated in the southern Indian Ocean. Data include (i) mea- surements from a well-ventilated room, (ii) a shaded thermo- graph, (iii) instruments housed in a manner broadly equiv- alent to a modern Stevenson screen, (iv) a set of measure- ments by a hygrometer mounted in a Stevenson screen, and for a much shorter period (v) two additional Stevenson screen configurations. All measurements were undertaken within an ∼ 80 m radius of each other. To our knowledge this is the first such multidecadal multi-instrument assessment of meteoro- logical instrument transition impacts ever undertaken, pro- viding potentially unique insights. The intercomparison also considers the impact of different ways of deriving daily and monthly averages. The long-term comparison is sufficient to robustly characterize systematic offsets between all the in- struments and seasonally varying impacts. Differences be- tween all techniques range from tenths of a degree Celsius to more than 1 ◦C and are considerably larger for maximum and minimum temperatures than for means or averages. System- atic differences of several tenths of a degree Celsius also exist for the different ways of deriving average and mean tempera- tures. All differences, except two average temperature series pairs, are significant at the 0.01 level using a paired t test. Given that all thermometers were regularly calibrated against a primary Kew standard thermometer maintained by the ob- servatory, this analysis highlights significant impacts of in- strument exposure, housing, siting, and measurement prac- tices in early meteorological records. These results reaffirm the importance of thoroughly assessing the homogeneity of early meteorological records.