[XeTeX] how to select fonts in math mode in plan TeX?

[Adam Russell]

Yes, after a bit more experimenting I understand that what you
posted is how it is done.
It seems that I only needed to change the first two "families". That is, 
\textfont0, scriptfont0,... and textfont1,....
But maybe my usage hasn't hit on where the other families might get 
used(i.e. more exotic symbols?).
Anyway, thank you for the help!

> Message: 4
> Date: Sun, 27 Mar 2011 10:41:36 +0100
> From: "John Was"<john.was at ntlworld.com>
> To: "Unicode-based TeX for Mac OS X and other platforms"
> 	<xetex at tug.org>
> Subject: Re: [XeTeX] how to select fonts in math mode in plan TeX?
> Message-ID:<6ECF8EFF827D482999A010A1829C3952 at k2010>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> 	reply-type=response
>
> Hello
>
> I think you want something analogous to the following (taken from some very
> old work in EmTeX):
>
> \textfont0=\wwimrten
> \scriptfont0=\wwimrseven
> \scriptscriptfont0=\wwimrfive
> \textfont1=\tximiten
> \scriptfont1=\tximiseven
> \scriptscriptfont1=\tximifive
> \textfont4=\tximiten
> \scriptfont4=\tximiseven
> \scriptscriptfont4=\tximifive
> \textfont5=\tximbiten
> \scriptfont5=\tximbiseven
> \scriptscriptfont5=\tximbifive
> \textfont6=\tximbten
> \scriptfont6=\tximbseven
> \scriptscriptfont6=\tximbfive
>
> The bits after the = signs are the various fonts that plain TeX will access
> in math mode.  After \txim (which was my abbreviation for 'Imprint tweaked
> for use in TeX' I have r for roman, i for italic, b for bold, and bi for
> bold italic.  At the end of the font names, I have 'five' for 5pt, 'seven'
> for 7pt, and 'ten' for 10pt.  If you follow this pattern for your preferred
> maths typeface (not necessarily using the same nomenclature) you should end
> up with roman, italic, bold, and bold italic for all the sizes that TeX will
> need to access in math mode.
>
> Of course, one can see why this isn't how it's usually done these days!
>
> John
>
>
>
>
> ----- Original Message -----
> From: "Adam Russell"<arussell at cs.uml.edu>
> To:<xetex at tug.org>
> Sent: 27 March 2011 03:36
> Subject: [XeTeX] how to select fonts in math mode in plan TeX?
>
>
>> When using xelatex I make use of the most excellent mathspec package.
>> However, I would like to do something similar in just plain xetex.
>> That is, how do I specify which font to use in math mode?
>> I tried the obvious which is:
>>      \font\cas="CaslonAntT"
>>      \cas puke %works! puke is typeset in the specified font
>>      $p=\int_0^1 f(x)\cas why is this not in the correct font?$
>> This, obviously,  is the way one would do it in plain TeX.
>> How to do the same thing in xetex?
>> Or, even better, how to globally set the math mode font?
>>