It is narrated from Sayyidah Asma bint Abi Bakr (may Allah be pleased with her) that in the time of the Messenger of Allah (peace and blessings be upon him) the people used to give Sadaqat al-Fitr by the same mudd with which the household measured its provisions, and all the people of Madinah did this.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20590