Reference for Bava Batra 9:2
הִנִּיחַ בָּנִים וּבָנוֹת וְטֻמְטוּם, בִּזְמַן שֶׁהַנְּכָסִים מְרֻבִּים, הַזְּכָרִים דּוֹחִין אוֹתוֹ אֵצֶל נְקֵבוֹת. נְכָסִים מֻעָטִין, הַנְּקֵבוֹת דּוֹחוֹת אוֹתוֹ אֵצֶל זְכָרִים. הָאוֹמֵר אִם תֵּלֵד אִשְׁתִּי זָכָר יִטֹּל מָנֶה, יָלְדָה זָכָר, נוֹטֵל מָנֶה. נְקֵבָה מָאתַיִם, יָלְדָה נְקֵבָה, נוֹטֶלֶת מָאתָיִם. אִם זָכָר מָנֶה אִם נְקֵבָה מָאתַיִם, וְיָלְדָה זָכָר וּנְקֵבָה, זָכָר נוֹטֵל מָנֶה וְהַנְּקֵבָה נוֹטֶלֶת מָאתָיִם. יָלְדָה טֻמְטוּם, אֵינוֹ נוֹטֵל. אִם אָמַר כָּל מַה שֶּׁתֵּלֵד אִשְׁתִּי יִטֹּל, הֲרֵי זֶה יִטֹּל. וְאִם אֵין שָׁם יוֹרֵשׁ אֶלָּא הוּא, יוֹרֵשׁ אֶת הַכֹּל:
If one left sons and daughters and a tumtum [one whose gender, male or female, is in doubt], the males "push him off" to the females, [saying to him: "Prove that you are a male and share" (with us in the inheritance)]. Where there is scant property, the females "push him off" to the males, [saying to him: "Prove that you are a female and be fed with us."] If one says: "If my wife bears a male, let him get one hundred," if she bore a male, he gets one hundred. [And even though we rule that "if one endows a fetus, it does not acquire," here we are speaking of a deathbed gift to one's son, a man being (more) favorably disposed towards his son (than to others)]. (If one says: "If my wife bears a female, (let her get) two hundred," if she bore a female, she gets two hundred. (If she said:) "If a male, one hundred; if a female, two hundred," if she bore a male and a female [twins], the male gets one hundred and the female, two hundred. If she bore a tumtum, it does not get anything. [This Mishnah is rejected, and the halachah is that a tumtum gets the least (amount) of the two.] If he said: "Whatever my wife bears, let him get…" (and it turns out to be a tumtum), it gets. And if there is no other heir, it inherits everything. [We might think that a tumtum is a distinct type of being and not fit to inherit; we are, therefore, apprised otherwise.]