May I suggest my solution ? (tested on Chrome v92+, Firefox v90+, Edge v92+).
A bit of box shadow :
#parchment {
position: absolute;
display: flex;
width: 75%;
min-height: calc((1vw + 1vh) * 75);
/* center page with absolute position */
top: 0%; left: 50%; transform: translate(-50%, 0);
margin: 2em 0;
padding: 4em;
box-shadow: 2px 3px 20px black, 0 0 60px #8a4d0f inset;
background: #fffef0;
filter: url(#wavy2);
}
and a bit of SVG feTurbulence as filter :
<div id="parchment"></div>
...
<svg>
<filter id="wavy2">
<feTurbulence x="0" y="0" baseFrequency="0.02" numOctaves="5" seed="1"></feTurbulence>
<feDisplacementMap in="SourceGraphic" scale="20" />
</filter>
</svg>
exemple there :
Old parchment with a mix of css and svg