That the Messenger of Allah stoned the Jamarat with pebbles like date sones or fingertips. (Using translation from Nasāʾī 3074)   

«أَمَرَنَا رَسُولُ اللَّهِ ﷺ فِي حَجَّةِ الْوَدَاعِ أَنْ نَرْمِيَ الْجَمْرَةَ بِمِثْلِ حَصَى الْخَذْفِ»  

The Messenger of Allah ﷺ hastened from al-Muzdalifah with a quite demeanour and ordered them (the people) to throw small pebbles and he hastened in the valley (wadi) of Muhassir. (Using translation from Abū Dāʾūd 1944)   

أَمَرَهُمْ رَسُولُ اللَّهِ ﷺ فَرَمَوْا بِمِثْلِ حَصَى الْخَذْفِ وَأَوْضَعَ فِي وَادِي مُحَسِّرٍ وَقَالَ «عَلَيْكُمُ السَّكِينَةَ»  

[Machine] "It is said that the Messenger of Allah ﷺ used to command us to throw the pebbles in an act of stoning called Jamrah similar to the size of hailstones. It was asked to Abu Muhammad (Abdul Rahman ibn Mu'adh), 'Does he have any companionship?' He said, 'Yes.'"  

«أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يَأْمُرُنَا أَنْ نَرْمِيَ الْجِمَارَ بِمِثْلِ حَصَى الْخَذْفِ» قِيلَ لِأَبِي مُحَمَّدٍ «عَبْدُ الرَّحْمَنِ بْنُ مُعَاذٍ لَهُ صُحْبَةٌ؟» قَالَ «نَعَمْ»