Siman 387
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א אָבֵל חַיָּב בִּכְפִיַּת הַמִּטָּה. וּבִשְׁעַת שֵׁנָה וַאֲכִילָה, יוֹשֵׁב עַל מִטָּה כְּפוּיָה, אֲבָל כָּל הַיּוֹם אֵינוֹ יוֹשֵׁב, אֲפִלוּ עַל מִטָּה כְּפוּיָה, אֶלָא עַל גַבֵּי קַרְקַע. וְכֵן הַמְנַחֲמִים אֵינָם רַשָּׁאִים לֵישֵׁב אֶלָא עַל גַבֵּי קַרְקַע.
1 A mourner is required to overturn the couch. When the time for sleeping or eating [arrives], he may sit [or sleep] on an overturned couch, but during the entire day he may not sit even on an overturned couch save on the ground. So too, the comforters are not permitted to sit save on the ground.
ב עַכְשָׁו לֹא נָהֲגוּ בִּכְפִיַּת הַמִּטָּה, מִפְּנֵי שֶׁיֹאמְרוּ הָעוֹבְדֵי כּוֹכָבִים שֶׁהוּא מְכַשְּׁפוּת, וְעוֹד שֶׁאֵין הַמִּטּוֹת שֶׁלָנוּ עֲשׂוּיוֹת כַּמִּטּוֹת שֶׁלָהֶן כְּדֵי שֶׁיְּהֵא נִכָּר בָּהֶם כְּפִיָּה.
2 Now it is not the common practice to overturn the couch because the Gentiles will say that it is [a kind] of sorcery. Moreover, our couches are not made like their couches in order that overturning should be discernible [as it was in former days].