<body>
<style>

div {
    position: absolute;
    left: 150px;
    top: 150px;
    height: 100px;
    width: 100px;
    background-color: black;
    transform: scale(2);
    will-change: transform;
}

.scale-down {
    transition-property: transform;
    transition-duration: 1s;
    transition-delay: calc(60 * 60s);
    transform: scale(1);
}

</style>
<div></div>
<script>

requestAnimationFrame(() => document.querySelector('div').className = "scale-down");

</script>    
</body>
