The spirit level was invented by Melchisedech Thevenot (born in either 1620 or 1621; died 1692). Thevenot was an amateur scientist and patron of many scientists and mathematicians. He was wealthy and well-connected, later becoming the Royal Librarian to King Louis XIV of France. Thevenot invented the instrument some time before February 2, 1661. This date can be very accurately established from Thevenot's correspondence with scientist Christiaan Huygens. Within a year of this date the inventor circulated details of his invention to others, including Robert Hooke in London and Vincenzo Viviani in Florence. It is occasionally argued that these bubble levels did not come into widespread use until the beginning of the eighteenth century, the earliest surviving examples being from that time, but Adrien Auzout had recommended that the Académie Royale des sciences take "levels of the Thevenot type" on its expedition to Madagascar in 1666. It is very likely that these levels were in use in France and elsewhere long before the turn of the century.
Thevenot is often confused with his nephew, the traveller Jean de Thevenot (born 1633; died 1667). There is evidence to suggest that both Huygens and Hooke later laid claim to the invention, although only within their own countries.