It is narrated from Nafi' (may Allah have mercy on him) that Ibn Umar (may Allah be pleased with them both) used to give dates as Sadaqat al-Fitr, except on one occasion when he gave barley.
Hadith Referenceمسند الإمام الشافعي / كتاب الزكاة / 669
Hadith Takhrijاخرجه البخارى الزكاة، باب صدقة الفطر على الحر والمملوك (1511)