Years ago I stumbled upon an article online (which for the life of me I have not been able to re-locate) about a fractional numbers system used by the stone cutters guilds in the medieval era in southwestern Spain or perhaps south eastern Portugal.

It was expressed as circles with various lines bisecting these circles and half-circles either vertical or horizontal in orientation. This symbols corresponded to fractions. Does anyone have a clue where to find information on this system?