The Prophet ﷺ used to pray two short rakahs after the witr while sitting.
حدثنا محمد بن بشار حدثنا حماد بن مسعدة حدثنا ميمون بن موسى المرئي عن الحسن عن أمه
أن النبي ﷺ كان يصلي بعد الوتر ركعتين خفيفتين وهو جالس
Sourcing, [sahih]. Tirmidhi collected it in Witr, chapter on what has been said about there being no two Witr prayers in one night, hadith 471, from Muhammad bin Bashshar with this chain, but its chain is daif. The hadith has corroborating narrations, see the following hadith.