מסכת כלים

פרק יח משנה א

NB:  For a wooden, leather or cloth utensil to be susceptible to tumah, it must be usually carried while full.  Thus, large containers with a capacity of 40 liquid se'ahs or 3 cubic cubits would normally be deemed tahor, as it was too heavy when full to carry.  

A bin (a large wooden box was used to store grain),

Beis Shammai say

is measured from the inside (to determine if its volume is more than 3 cubic cubits ),

and Beis Hillel say

it is measured from the outside (and the thickness of its walls will be counted as part of its capacity);

they agree with each other

that the thickness of the legs (that project below the bottom of the bin) and the thickness of the rims (which project above the walls of the bin) are not counted;

Rabbi Yosi says

they agree that the thickness of the legs

and the thickness of the rims are measured,

and [the space] between them [the legs] is not measured;

Rabbi Shimon Shezuri says,

if the legs were

one handbreadth high (that is, if they raised the bottom of the bin that high off the ground)

and [the space] between them [the legs] is not measured,

and if not,

and [the space] between them [the legs] is measured.

It's base (this was a base or stand that the bin of the previous mishnah; note that there are several other interpretations of this term)

when it is removeable,

is not [considered to be] attached to it (such that even if the bin is not susceptible to tumah, the base can be),

and is not measured with it,

and does not protect with it by the canopy of a corpse (a covered bin of over three cubic cubits can serve to shield objects within it from tumah when passing over a grave; in this case, the bin would shield, but the base would not)

and we may not drag it [the base] on shabbos

when there is money inside it (as it is a base for something forbidden, it is muktzeh);

and if it is not removable,

it is [considered to be] attached to it,

and is measured with it,

and does protect with it by the canopy of a corpse

and we may drag it [the base] on shabbos

even though there is money in it (as the base is considered primarily a base for the bin, and not the forbidden money).

It's cover (which extended above the top of the bin, but shelters only part of the bin),

when it is permanently set in place,

is considered attached to it,

and is measured with it,

and if it is not permanently set in place,

is not considered attached to it,

and is not measured with it.

How do we measure it? (as the cover is only over part of the bin, the question is does the airspace above the bin that is not under the cover get counted towards its volume as well?)

[by imagining] a diagonal line (this line runs from the top of the cover at the edge that is over the middle of the bin to the top of the opposite, uncovered rim of the bin; the space below that line is counted towards the volume);

Rabbi Yehuda says

if it [the bin] cannot stand on its own

it is tahor (even if it's volume is less than three cubic cubits).