One of those mathematicians was Abū al-Hasan ibn Alī al-Qalasādī (1421–1486).
The symbol was first seen in print without the vinculum (the horizontal "bar" over the numbers inside the radical symbol) in the year 1525 in Die Coss by Christoff Rudolff, a German mathematician.
[3] The Unicode and HTML character codes for the radical symbols are: However, these characters differ in appearance from most mathematical typesetting by omitting the overline connected to the radical symbol, which surrounds the argument of the square root function.
The OpenType math table allows adding this overline following the radical symbol.
[18] Additionally a "Radical Symbol Bottom" (U+23B7, ⎷) is available in the Miscellaneous Technical block.