Carl Linnaeus a rare book, if he let Linnaeus stay with him, and Burman accepted. On 24 September 1735, Linnaeus moved to Hartekamp to become personal physician to Clifford, and curator of Clifford's herbarium. He was paid 1,000 florins a year, with free board and lodging. Though the agreement was only for a winter of that year, Linnaeus practically stayed there until 1738. It was here that he wrote a book "Hortus Cliffortianus", in the preface of which he described his experience as "the happiest time of my life." (A portion of Hartekamp was declared as public garden in April 1956 by
Carl Linnaeus the idea of a hierarchical structure of classification which is based upon observable characteristics and intended to reflect natural relationships. While the underlying details concerning what are considered to be scientifically valid "observable characteristics" have changed with expanding knowledge (for example, DNA sequencing, unavailable in Linnaeus' time, has proven to be a tool of considerable utility for classifying living organisms and establishing their evolutionary relationships), the fundamental principle remains sound. Linnaeus' system of taxonomy was especially noted as the first to include humans ("Homo") taxonomically grouped with apes ("Simia"), under the header of "Anthropomorpha". German biologist Ernst Haeckel speaking in