One should say Takbir while going in prostration.

Narrated Abu Bakr bin 'Abdur Rahman Ibn Harith bin Hisham and Abu Salama bin 'Abdur Rahman: Abu Huraira used to say Takbir in all the prayers, compulsory and optional -- in the month of Ramadan or other months. He used to say Takbir on standing for prayer and on bowing;
then he would say, "Salmi'a-l-lahu Liman hamida," and before prostrating he would say "Rabbana walaka-l-hamd." Then he would say Takbir on prostrating and on raising his head from the prostration, then another Takbir on prostrating (for the second time), and on raising his head from the prostration. He also would say the Takbir on standing from the second Rak'a. He used to do the same in every Rak'a till he completed the prayer. On completion of the prayer, he would say, "By Him in Whose Hands my soul is! No doubt my prayer is closer to that of Allah's Apostle than yours, and this was His prayer till he left this world." And Abu Huraira said, "When Allah's Apostle raised his head from (bowing) he used to say "Sami' a-l-lahu Liman hamida, Rabbana walakal-hamd." He Would invoke Allah for some people by naming them: "O Allah! Save Al-Walid bin Al-Walid and Salama bin Hisham and 'Aiyash bin Abi Rabi'a and the weak and the helpless people among the faithful believers O Allah! Be hard on the tribe of Mudar and let them suffer from famine years like that of the time of Joseph." In those days the Eastern section of the tribe of Mudar was against the Prophet.

حَدَّثَنَا أَبُو الْيَمَانِ، قَالَ حَدَّثَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ أَخْبَرَنِي أَبُو بَكْرِ بْنُ عَبْدِ الرَّحْمَنِ بْنِ الْحَارِثِ بْنِ هِشَامٍ، وَأَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ أَنَّ أَبَا هُرَيْرَةَ، كَانَ يُكَبِّرُ فِي كُلِّ صَلاَةٍ مِنَ الْمَكْتُوبَةِ وَغَيْرِهَا فِي رَمَضَانَ وَغَيْرِهِ، فَيُكَبِّرُ حِينَ يَقُومُ، ثُمَّ يُكَبِّرُ حِينَ يَرْكَعُ، ثُمَّ يَقُولُ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ. ثُمَّ يَقُولُ رَبَّنَا وَلَكَ الْحَمْدُ. قَبْلَ أَنْ يَسْجُدَ، ثُمَّ يَقُولُ اللَّهُ أَكْبَرُ. حِينَ يَهْوِي سَاجِدًا، ثُمَّ يُكَبِّرُ حِينَ يَرْفَعُ رَأْسَهُ مِنَ السُّجُودِ، ثُمَّ يُكَبِّرُ حِينَ يَسْجُدُ، ثُمَّ يُكَبِّرُ حِينَ يَرْفَعُ رَأْسَهُ مِنَ السُّجُودِ، ثُمَّ يُكَبِّرُ حِينَ يَقُومُ مِنَ الْجُلُوسِ فِي الاِثْنَتَيْنِ، وَيَفْعَلُ ذَلِكَ فِي كُلِّ رَكْعَةٍ حَتَّى يَفْرُغَ مِنَ الصَّلاَةِ، ثُمَّ يَقُولُ حِينَ يَنْصَرِفُ وَالَّذِي نَفْسِي بِيَدِهِ إِنِّي لأَقْرَبُكُمْ شَبَهًا بِصَلاَةِ رَسُولِ اللَّهِ ﷺ إِنْ كَانَتْ هَذِهِ لَصَلاَتَهُ حَتَّى فَارَقَ الدُّنْيَا.