Source text
وَالْغَلَبَةُ فِي الْمَائِعِ الَّذِي لَا وَصْفَ لَهُ كَالْمَاءِ الْمُسْتَعْمَلِ... تَكُونُ بِالْوَزْنِ
• Used water does not have a different color, taste, or smell by which it can be distinguished from Absolute Water. Its dominance is therefore judged by weight.
• 2 ratls of Used Water + 1 ratl of Absolute Water → Used Water dominates → not valid for Wudu.
• 1 ratl of Used Water + 2 ratls of Absolute Water → Absolute Water dominates → valid for Wudu.
• Ratl is the traditional unit used by the text; the point here is the relative proportion, not conversion to a modern unit.