

The linea (meaning line) was a unit of length or distance in the old Castilian system of units. Since no actual Castilian standards are definitively known by the present day, the only way of determining the length of any Old Castilian unit would be to measure something in modern terms whose length was given by the Castilians in their units. And because this procedure does not give us any clue to which unit may have been the base unit and which were subsidiary units, this distinction really does not apply to the Old Castilian units here given, so all the units really have equal status. However, most references appear to have treated the vara (Castilian yard) as the base unit, expressing other units in terms of the vara.
Value in terms of the varaEdit
The linea was equal to ^{1}/_{576} vara, according to Cardarelli^{[1]}. The table in Woolhouse^{[2]} implies a length of ^{1}/_{432} vara.
Relation to other Old Castilian unitsEdit
 According to Cardarelli^{[1]}:
 According to Woolhouse^{[2]}
Value in terms of modern unitsEdit
Based on the figure of 0.835905 m for the length of the vara, given by Cardarelli in his tabulation^{[1]}, the linea was 0.001451224 m = 0.0571348 in. Other values of the vara^{[3]} have been found in the literature as well, differing slightly from Cardarelli's, which would lead to slightly different values for the length of the linea.
Woolhouse^{[2]} gives a value of 0.077 in (0.1956 cm) in his tabulation.
ReferencesEdit
 ↑ Cardarelli, François (1998). Scientific Unit Conversion. Berlin, Heidelberg, New York: SpringerVerlag. ISBN 3540760229.
 ↑ Woolhouse, Wesley Stoker Barker (1864). London, England: Virtue Brothers & Co. (Reprinted by Kessinger Publishing).
 ↑ The variable vara (length of the vara in Spain and various former colonies)