Kurdus narrates: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) used to say nine takbirs each in the prayers of Eid al-Fitr and Eid al-Adha. At the very beginning he would say four takbirs, then recite, then say one takbir and go into ruku' with it. Then he would stand for the second rak'ah, recite first, then say four takbirs, going into ruku' with one of them.
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are thiqat (trustworthy).