Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) says: When the sun was eclipsed in the time of the Prophet (peace and blessings be upon him), it was announced: "The prayer is about to be held." The Messenger of Allah (peace and blessings be upon him) performed two bowings (ruku') in one rak'ah. Then he stood and performed two bowings in one rak'ah, then he sat, and the eclipse had ended.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخسوف / 6300
Urwah narrates from Sayyidah Aishah (may Allah be pleased with her): The sun lost its light in the time of the Prophet (peace and blessings be upon him), so the Prophet (peace and blessings be upon him) sent a caller to announce: "Gather for the prayer," and the people gathered. He (peace and blessings be upon him) led them in two rak'ahs with four bowings and four prostrations, then recited the tashahhud and gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخسوف / 6301