Related for Berakhot 1:2
מֵאֵימָתַי קוֹרִין אֶת שְׁמַע בְּשַׁחֲרִית. מִשֶּׁיַּכִּיר בֵּין תְּכֵלֶת לְלָבָן. רַבִּי אֱלִיעֶזֶר אוֹמֵר, בֵּין תְּכֵלֶת לְכַרְתִּי. וְגוֹמְרָהּ עַד הָנֵץ הַחַמָּה. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, עַד שָׁלֹשׁ שָׁעוֹת, שֶׁכֵּן דֶּרֶךְ בְּנֵי מְלָכִים לַעֲמֹד בְּשָׁלֹשׁ שָׁעוֹת. הַקּוֹרֵא מִכָּאן וְאֵילָךְ לֹא הִפְסִיד, כְּאָדָם הַקּוֹרֵא בַתּוֹרָה:
From which time may the Shema be recited in the morning? When it is possible to distinguish between the tcheleth (blue) and the white. [between the strands of tcheleth and the strands of white in the tzitzith. That is, after the shearing of the wool, which is dyed tcheleth, there are places where the dye does not take well and which remain white.] R. Eliezer says: Between tcheleth and leek-green. [The color of tcheleth is close to the green of leeks.] And the time of its recital is until sunrise. R. Yehoshua says: Until the third hour [of the day. Until the end of the third hour, which is one-quarter of the day when the days and the nights are equal. And the time of the recital of the Shema is always until one-quarter of the day, whether the days are long or short. Similarly, in (Chapter 4, Mishnah 1): "The time of the morning prayer is until the fourth hour of the day," the meaning is until one-third of the day, "the fourth hour" being mentioned because one-third of the day is four hours long when the days and nights are equal. Whenever the Mishnah mentions "thus and thus hours of the day," it is to be understood along these lines. I understand this to be Rambam's interpretation and I accept it. The rationale for R. Yehoshua's "Until the third hour of the day" is that usually the sons of kings do not rise from their beds until the end of the third hour; and the intent of the Torah in "and when you rise" is until the time when all men have risen from their beds. And the halachah is in accordance with R. Yehoshua. However, ab initio, one should attempt to synchronize the recital of Shema with sunrise, as the vatikim ("the early saints") did.], it being the custom of the sons of kings to rise at the third hour. One who recites it after this time does not forfeit anything thereby [that is, he does not forfeit the blessing before and after; but even though he goes beyond its time, he recites it along with the blessing before and after], as one who reads in the Torah. [Even though he did not recite the Shema in its designated time, he receives reward as one who reads in the Torah.]