Tosefta for Ketubot 6:3
פָּסְקָה לְהַכְנִיס לוֹ אֶלֶף דִּינָר, הוּא פוֹסֵק כְּנֶגְדָּן חֲמִשָּׁה עָשָׂר מָנֶה. וּכְנֶגֶד הַשּׁוּם, הוּא פוֹסֵק פָּחוֹת חֹמֶשׁ. שׁוּם בְּמָנֶה וְשָׁוֶה מָנֶה, אֵין לוֹ אֶלָּא מָנֶה. שׁוּם בְּמָנֶה, הִיא נוֹתֶנֶת שְׁלֹשִׁים וְאֶחָד סֶלַע וְדִינָר. וּבְאַרְבַּע מֵאוֹת, הִיא נוֹתֶנֶת חֲמֵשׁ מֵאוֹת. מַה שֶּׁחָתָן פּוֹסֵק, הוּא פוֹסֵק פָּחוֹת חֹמֶשׁ:
If she committed herself to bring in to him (as dowry) one thousand dinars, he designates them as fifteen manah. [One thousand dinars are ten manah; and when the groom comes to accept it and to write it in the kethubah, he writes one-third more, which is fifteen manah (If the bride brought in to him actual dinars; for he earns through them.)] And relative to assessment, he designates a fifth less. [If she brought in to him clothing and jewelry which need to be assessed, he writes (in the kethubah) a fifth less (than the assessment). For example, if she brought in an assessment of one thousand zuz, he acknowledges only eight hundred. For it is the practice of the assessors of the bride's property to assess it at more than its worth to lend distinction to the bride and to endear her to her husband.] If the assessment were a manah and the worth a manah, [that is, if they assessed the bride's property at its actual worth in the marketplace], he has only one manah. [They write in the kethubah only a manah, as they assessed it.] (For) an assessment of a manah, she gives thirty-one sela and a dinar. [For an assessment that he accepts as a manah, i.e., where they told him: Write a manah in the kethubah, and she will bring in to you the worth of a manah, it must be assessed in the bridal chamber as thirty-one sela and a dinar, which is a manah and a fifth.] And for four manah, she gives five manah. [When the groom took upon himself to write four manah, she gives five manah according to the estimate of the assessors.] Whatever the groom writes, he writes a fifth less. [If they assessed it first, and she brought it in to him, whether a small assessment or a large one, he writes a fifth less.]