Responsa for Menachot 74:4
ר' חייא ורב אחא בריה דרב אויא מכוין ומנח ליה להדי ליביה רב אשי הוה יתיב קמיה דאמימר הוה ציריא בידיה וקא מתחזיין תפילין אמר ליה לא סבר לה מר לך לאות ולא לאחרים לאות אמר ליה במקום לך לאות איתמר
Since the Torah ordains that one must put tefillin upon the hand and also upon the head, as in the latter case it is to be upon the upper part of the head so in the former it is to be upon the upper part of the hand. R'Eliezer says, This is unnecessary; for the verse says, 'And it shall be for a sign unto thee upon thy hand', implying that the sign shall be unto thee but not unto others.<span class="x" onmousemove="('comment',' And if actually put on the hand it would immediately be noticeable by all. It must consequently be put high up on the arm which part is usually covered with the sleeve.');"><sup>6</sup></span>
Teshuvot Maharam
A. He should fasten a board beneath the seat (within not more than three tefahim below the latrine walls) so that the feces first fall on the board and then into the ditch. Should the board break on the Sabbath, he would still be permitted to use the latrine on that day.
SOURCES: Cr. 178, 179; Pr. 96; L. 349; Mord. Shabb. 376; Hag. Mord. Shabb. 461; Tashbetz 38; Hag. Maim., Shabbat 15, 4; Kol Bo 31 (p. 34a). Cf. Terumat Hadeshen 66.