Mercury-in-glass thermometer ushered in a new era of accuracy and precision in thermometry, and is still to this day regarded as one of the most accurate thermometers available. The thermometer was used by the originators of the Fahrenheit and Celsius scales. Anders Celsius, a Swedish scientist, devised the Celsius scale, which was described in his publication "The origin of the Celsius temperature scale" in 1742. Celsius used two fixed points in his scale: the temperature of melting ice and the temperature of boiling water. This wasn't a new idea, since Isaac Newton was already working on something similar. The distinction of Celsius
International Temperature Scale of 1990 record cold temperature achieved by the NIST in 1994). Estimates of the differences between thermodynamic temperature and the ITS–90 ("T"-"T") were published in 2010. It had become apparent that ITS–90 deviated considerably from PLTS-2000 in the overlapping range of 0.65 K to 2 K. To address this, a new He vapor pressure scale was adopted, known as PTB-2006. For higher temperatures, expected values for "T"-"T" are below 0.1 mK for temperatures 4.2 K – 8 K, up to 8 mK at temperatures close to 130 K, at 0 K (by definition) at the triple point of water (273.16 °C), but