Convert from gry to X unit

Unit Definition (gry)
The gry is a proposed unit of distance in the English traditional system. The name was first used in June 1679 by the philosopher John Locke (1632-1704) as a unit equal to 0.001 foot, 0.01 inch, or 0.1 line in a decimalized distance system. (Thomas Jefferson, who was very familiar with Locke's writings, later proposed a similar system in the U.S., but he called 0.001 foot a point rather than a gry.) In 1813, the gry was revived in another decimal measurement scheme in Britain. All these ideas failed, but the gry had some limited use in the nineteenth century as a unit equal to 0.1 line or 1/120 inch (0.211 667 millimeter). Long forgotten, the gry recently came back into the limelight in connection with a puzzle, circulating on the Internet, which asked for three English words ending in -gry. The word "gry" is from the ancient Greek, where it meant "a trifling amount".

Unit Definition (X unit)
The X-unit (symbol xu) is a unit of length formerly used to measure the wavelength of X-rays and gamma rays. The X-unit is approximately 1.0021×10-13 metre. Defined by the Swedish physicist Karl Manne Georg Siegbahn (1886-1978) in 1925, the X-unit could not at that time be measured directly; the definition was instead made in terms of the spacing between planes of the calcite crystals used in the measuring apparatus.