The mithqual is a unit of wieght used in Baha'i sacred writings, often to describe legal features such as the maximum allowable size of dowries and fines. The following text is taken from the glossary of the Kitab-i-Aqdas (Most Holy Book) as published by the Baha'i World Centre in 1992:

A unit of weight, equivalent to a little over 3 1/2 grammes, used in the Kitab-i-Aqdas with reference to quantities of gold or silver for various purposes, usually in amounts of 9, 19 or 95 mithqals. The equivalents of these in the metric system and in troy ounces (which are used in the measurement of precious metals), are as follows:

9 mithqals = 32.775 grammes = 1.05374 troy ounces
19 mithqals = 69.192 grammes = 2.22456 troy ounces
95 mithqals = 345.958 grammes = 11.12282 troy ounces

This computation is based on the guidance of Shoghi Effendi, conveyed in a letter written on his behalf, which states "one mithqal consists of nineteen nakhuds. The weight of twenty-four nakhuds equals four and three-fifths grammes. Calculations may be made on this basis." The mithqal traditionally used in the Middle East had consisted of 24 nakhuds but in the Bayan this was changed to 19 nakhuds and Baha'u'llah confirmed this as the size of the mithqal referred to in the Baha'i laws.