Musannaf Ibn Abi Shayba 3:3327

Ibn Idris narrated to us, from Ibn Jurayj, from ‘Ata’, from Ibn ‘Abbas, that he used to say the Takbir in the ‘Eid prayer: in the first [rak'ah], seven Takbirs including the opening Takbir; and in the last [rak'ah], six [Takbirs] including the Takbir of the rak'ah. All of them were before the recitation.