Swiss chemist Nicolas Théodore de Saussure was born #OTD in 1767.
His book Recherches chimiques sur la Végétation (1804) was the first summation of the fundamental process of photosynthesis and a major contribution to the understanding of plant physiology. In contrast to some of his predecessors in the field of photosynthesis research, Saussure based his conclusions on extensive quantitative data that he had collected.
https://en.wikipedia.org/wiki/Nicolas_Th%C3%A9odore_de_Saussure