It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that on the day of the solar eclipse the Messenger of Allah (peace and blessings be upon him) prayed four bowings (ruku') in two units (rak'ahs), with four prostrations.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10599