Mishnayos Kesuvos Perek 5 Mishnah 1

Although they said as a principle that a virgin collects two hundred dinars as payment for her marriage contract and that a widow collects one hundred dinars, if the husband wishes to add even an additional ten thousand dinars, he may add it. If she is then widowed or divorced, whether from betrothal or whether from marriage, she collects the entire amount, including the additional sum. Rabbi Elazar ben Azarya says: If she is widowed or divorced from marriage, she collects the total amount, but if she is widowed or divorced from betrothal, a virgin collects two hundred dinars and a widow one hundred dinars. This is because he wrote the additional amount for her in the marriage contract only in order to marry her. Rabbi Yehuda says a related halakha with regard to the marriage contract: If he wishes, he may write for a virgin a document for two hundred dinars as is fitting for her, and she may then write a receipt stating: I received one hundred dinars from you. Even though she has not actually received the money, the receipt serves as a means for her to waive half of the amount due to her for her marriage contract. According to Rabbi Yehuda, the financial commitment in the marriage contract is a right due to the wife, which she may waive if she chooses to do so. And similarly, for a widow he may write one hundred dinars in the contract and she may write a receipt stating: I received from you fifty dinars. However, Rabbi Meir says: It is prohibited to do this, as anyone who reduces the amount of the marriage contract to less than than two hundred dinars for a virgin or one hundred dinars for a widow, this marital relationship amounts to licentious sexual relations because it is as if he did not write any marriage contract at all.