Reference for Shabbat 17:6
הָאֶבֶן שֶׁבְּקֵרוּיָה, אִם מְמַלְּאִין בָּהּ וְאֵינָהּ נוֹפֶלֶת, מְמַלְּאִין בָּהּ. וְאִם לָאו, אֵין מְמַלְּאִין בָּהּ. זְמוֹרָה שֶׁהִיא קְשׁוּרָה בְטָפִיחַ, מְמַלְּאִין בָּהּ בְּשַׁבָּת:
The stone in a [dry] gourd [which is used for drawing water. Because it is light, it does not sink but floats, so that a stone is put into it to weight it] — if it [the gourd] is filled and it [the stone] does not fall out, [it being well fixed in the mouth of the gourd, in which instance it is regarded as a vessel], it is filled; if not, it is not filled. [It is like other stones and the gourd may not be moved, being a base for the stone that it carries.] A rod which is attached to a tafiach [a small jug with which water is drawn from a well or a spring] may be filled on Shabbath, [for the rod is regarded as a vessel].