The eighth and final perek of Massekhet Shekalim follows the mishnayot of the previous perek, which discussed money that was found in the Temple and in Jerusalem, and whether that money is to be considered consecrated to the Mikdash (Temple) or not. These mishnayot deal with other things that are found in Jerusalem; in this case the question is whether they are to be considered ritually pure or defiled.
One case, for example, is utensils that are found in the city. According to Rabbi Meir, if they are found in a place that leads to a mikveh, where such utensils are taken to purify them, we must assume that they are tameh (ritually impure), but if they are found on the path leading away from the mikveh, we can assume that they were already dipped and are considered ritually pure.
Archaeological excavations have found many mikva’ot like the ones described here, in which there are separate staircases leading into the mikveh and leading away from it, with a clear separation between them. They were set up this way in order to ensure that the people going in to the mikveh who are tameh, should not touch the ones who were leaving the mikveh, already tahor (ritually pure).
However, Rabbi Yose says: They are all ritually pure, except for the basket, and the shovel, and the meritza, which are specifically used for graves, to gather up the bones of the dead. These tools must be presumed to be ritually impure, but in general, vessels are presumed to be pure.
During the Second Temple period people were buried in temporary graves and after their flesh decomposed their bones were moved to permanent family burial caves. The basket was a special one that was used to collect the bones. The shovel had a wide head and a long handle, held in both hands; when associated with a basket, as it is here, it was used for digging as well as the collection of bones for burial. The meritza in this context was a tool similar to a pickax, also called a dolabra, with which one could extract large stones and then push them into place to close a burial cave.
The Rambam rules like Rabbi Yose, that utensils in Jerusalem are not automatically assumed to be tameh, since the Rabbinic ordinance that such utensils are tameh that was applied in other cities (see the Mishna in Taharot 4:5) was not applied in Jerusalem.