The spices were weighed. The oil was gathered from the twelve tribes. But the mixture itself required something the Torah calls "the work of the perfumer." Targum Pseudo-Jonathan preserves the phrase precisely: the oil was to be perfumed with perfume, the work of the perfumer, of compounded perfumes — a triple emphasis on craft (Exodus 30:25).
Why name the perfumer at all?
The midrashic tradition (Bereshit Rabbah 91:3, c. 450 CE) noted that the Torah names three crafts by the Spirit of God: the weaver, the stonecutter, and the perfumer. These were the only skills considered so refined that Israel could not assume them — they had to be given from above. The perfumer's art required not just knowledge of proportions but the trained nose, the steady hand, the patience to let the mixture rest between compoundings.
This is why the sages insisted that the holy anointing oil was not merely blended. It was compounded — layered, aged, worked until the molecules of myrrh and cinnamon and calamus and cassia no longer held distinct identities but became a single new substance. The oil that emerged was not "oil with spices in it." It was a new creation, as different from its ingredients as bread is from flour.
This is also why the Torah forbade duplicating the recipe for private use. The list of ingredients was public — anyone could read it in Exodus 30. But the work of the perfumer was not transmissible by recipe alone. The oil of Moses' day carried the hands of its maker and the Presence of God who had given the craft. Counterfeits could match the weights and still miss the fragrance.
The Maggid takes this home: holy things cannot be reproduced from the ingredient list alone. You need the perfumer's hands. You need the time. You need the Spirit that gives the craft.