He was not entirely joking.  Charles Dickens reports drinking 
Mississippi River water while in St. Louis.  This event with Twain also 
occurred in St. Louis in April of 1882, at the outset of his return to 
the Mississippi.  Thank you, Taylor, for the reference. It also serves 
to indicate that the muddy nature of the Mississippi River derives from 
the Missouri River, often referred to as "The Big Muddy",  an appelation 
mistakenly applied to the Mississippi on occasion.

On 9/9/22 10:04, Taylor Roberts wrote:
>  From LOM ch 22 (surely a joke!):
>
> 'What is a person to do here when he wants a drink of water?—drink this
> slush?'
>
>
> 'Can't you drink it?'
>
>
> 'I could if I had some other water to wash it with.'
>
>
> Here was a thing which had not changed; a score of years had not affected
> this water's mulatto complexion in the least; a score of centuries would
> succeed no better, perhaps. It comes out of the turbulent, bank-caving
> Missouri, and every tumblerful of it holds nearly an acre of land in
> solution. I got this fact from the bishop of the diocese. If you will let
> your glass stand half an hour, you can separate the land from the water as
> easy as Genesis; and then you will find them both good: the one good to
> eat, the other good to drink. The land is very nourishing, the water is
> thoroughly wholesome. The one appeases hunger; the other, thirst. But the
> natives do not take them separately, but together, as nature mixed them.
> When they find an inch of mud in the bottom of a glass, they stir it up,
> and then take the draught as they would gruel. It is difficult for a
> stranger to get used to this batter, but once used to it he will prefer it
> to water. This is really the case. It is good for steamboating, and good to
> drink; but it is worthless for all other purposes, except baptizing.
>
>
>
> On Fri, Sep 9, 2022 at 12:47 PM Dave Davis<[log in to unmask]>
> wrote:
>
>> I think no one in their right mind would fill a glass with it -- except for
>> demonstration purposes -- below Minneapolis/St. Paul. (I've seen it there
>> -- it is still mostly clear.
>>
>> On Fri, Sep 9, 2022 at 12:44 PM Scott Holmes<[log in to unmask]>
>> wrote:
>>
>>> I suspect I could search this out in his autobiography but Twain-L may
>>> be quicker - Did he ever mention drinking Mississippi River water?  If
>>> so, when might this have occurred?  This is certainly not something
>>> anyone would choose to do today but in the eighteenth (pre-industrial)
>>> century this was considered as quite healthful.
>>>
>>> --
>>> /Unaffiliated Geographer and Twain aficionado/
>>>
-- 
/Unaffiliated Geographer and Twain aficionado/