Qataadah bin Da'aamah As-Sadusi relates:
"I asked Anas R.A., 'How was the hair of Rasulullah (ﷺ)?'. He replied: 'It was not very twisted, nor very straight. It had a slight twist and was a bit curled, and reached till his ear-lobes'".
English reference: Book 3, Hadith 26
Arabic reference: Book 3, Hadith 27