Alqamah bin Abi Alqamah narrates from his mother, who was the freed slave-woman of the Mother of the Believers Aishah (may Allah be pleased with her), that she said that Sayyidah Aishah (may Allah be pleased with her) said: Women used to send me small boxes containing cotton on which there was yellowness from menstrual blood, and I would say: Do not be hasty until you see the clear white discharge.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1589