The Sextant was among the new constellations proposed in the Hevelius Uranographia (1680), the most detailed and influential celestial atlas of its time. Although Johann Hevelius was the only author listed on the title page, Johann regarded his wife, Elisabeth, as an astronomer in her own right. They worked together in the observatory of their Gdansk home to measure angular widths and distances with the sextant.  A single measurement with the sextant required two observers.  

See the Introduction to the Sextant; and the star atlas of Hevelius.