Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) as marfu' that he (peace and blessings be upon him) said: "There is no zakah on less than five wasq, and a wasq is sixty sa'."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7427
Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: A wasq is sixty sa'. Yahya said: I asked Sharik about it, and he said: I do not remember it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7428
Ya'qub bin al-Qa'qa' (may Allah have mercy on him) said that Ata (may Allah have mercy on him) said: Zakah is due on five wasq, and that is three hundred sa'; and a wasq is sixty sa'.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7430