Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that in the time of the Messenger of Allah (peace and blessings be upon him) the people used to give sadaqat al-fitr as a sa' of barley, or a sa' of dates, or a sa' of raisins, or a sa' of hulless barley (sult).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7700