Changing widths of specific columns in my long table

I’m dealing with a large table in my thesis.

I currently have four columns in my table, with small numbers in the 1st and 4th columns and long(ish) text in columns 2 and 3. Therefore I want columns 1 and 4 to be narrower than 2 and 4.

I have referred to the tabularx (I’ve been told it is also applicable to xltabular) documentation where it says:

{>{hsize=.5hsizelinewidth=hsize}X
>{hsize=1.5hsizelinewidth=hsize}X}

to change the X column sizes, but how would I do this for four columns?

My current table uses the following:

begin{xltabular}{linewidth}{XXXX}
   
  
    hline
        thead{Approx.  Raman shift $(cm^{-1})$} & textbf{Assignment} & thead{What does this  mean for bone?} & textbf{References}  hline

*Main body of table*
 end{xltabular}

I have referred to Table layout with tabularx (column widths: 50%|25%|25%), but it didn’t help.

Many thanks