Sayyidah Maymunah (may Allah be pleased with her) said: "The Messenger of Allah (peace and blessings be upon him) would pray on a khumrah (small prayer mat), which would be spread out for him (peace and blessings be upon him) in the mosque."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20377