Al-Aswad, Alqamah and Masruq report that Sayyiduna Abdullah (may Allah be pleased with him) used to say nine takbirs in Eid al-Adha and Eid al-Fitr: he would stand and say four takbirs, then recite, then say one takbir and bow with it; then he would stand and recite, and say four takbirs and bow with one of them.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9485