Planetary Days and Hours: How Alchemists Timed Their Work (and Whether You Should)

Stand outside before dawn on a Wednesday. Not metaphorically. Actually do it. Feel the specific quality of that darkness — the hour before the sun crests, when the air is still cold from the night and nothing has started yet. Medieval spagyrists would have been awake already. They would have known, with precision, not just that it was Wednesday, but which planetary hour they were standing inside. They would have known whether this was the moment to harvest, to fire the athanor, to press the first tincture, or to wait. And they would not have considered any of that superstition. They would have considered it craft.

The planetary hours system is one of the most persistently misunderstood elements of the hermetic herbal tradition. Modern readers tend to approach it one of two ways: either they dismiss it as medieval fantasy that we’ve thankfully outgrown, or they adopt it wholesale as a kind of magical scheduling app, timing their chamomile harvest by a phone app with moon phases. Both responses miss the point. To understand what the alchemists were actually doing — what Paracelsus meant, what the Picatrix encodes, what spagyrists from the sixteenth century onward were calculating at their benches — you need to understand the system on its own terms first.

Planet	Day of Week	Metal	Organ
Saturn	Saturday	Lead	Spleen
Jupiter	Thursday	Tin	Liver
Mars	Tuesday	Iron	Gallbladder
Sol	Sunday	Gold	Heart
Venus	Friday	Copper	Kidneys
Mercury	Wednesday	Quicksilver	Lungs
Luna	Monday	Silver	Brain

The Architecture of Planetary Time

The system is ancient. Its roots run back to Hellenistic astrology, and its clearest early formulations appear in texts like the Tetrabiblos of Claudius Ptolemy (second century CE) and in the astrological sections of the Greek magical papyri. The basic structure is this: each day of the week is ruled by one of the seven classical planets — Saturn, Jupiter, Mars, Sol, Venus, Mercury, Luna. You already live inside this system without knowing it. Saturday is Saturn’s day. Sunday is Sol’s. Monday is Moon’s day. Wednesday is Mercredi in French, Mercury’s day. The Norse planet-gods replaced the Roman ones in English, but the structure is identical and unbroken.

Within each day, the hours are further divided. There are twenty-four hours in a day, and each is assigned to a planet in a fixed sequence. The sequence is the Chaldean order: Saturn, Jupiter, Mars, Sol, Venus, Mercury, Luna — and then it repeats. The planet ruling the first hour of any given day is the same planet that rules the day itself. So on Wednesday, the first hour belongs to Mercury. Work through the Chaldean sequence for twenty-four hours, and you’ll find that the planet ruling the twenty-fifth hour — which is the first hour of the next day — is the Moon. Hence Thursday, Moon’s day shifted: actually it lands on Jupiter in the sequence, making Thursday Jove’s day, Jeudi in French. The arithmetic is internally consistent. This is not random folklore. Someone sat down and worked it out.

What Spagyrists Did With It

Paracelsus — Theophrastus Bombastus von Hohenheim, working in the early sixteenth century — built his entire medical cosmology on the doctrine of correspondences. Each planet governed a metal, a bodily organ, a class of disease, and a family of plants. Sol ruled gold and the heart. Luna ruled silver and the brain. Saturn ruled lead and the spleen. Mercury ruled quicksilver and the lungs. The correspondences weren’t decorative. They were, for Paracelsus, causal. The same principle that animated a planet animated the plant under its rulership. When you worked with that plant — harvested it, fermented it, calcined its salt — you were engaging directly with that planetary force. Timing, therefore, was not incidental. It was the frame inside which the work became coherent.

In practice, this shaped spagyric operations from the ground up. Harvesting a solar plant like Saint John’s Wort ideally happened on a Sunday, during a solar hour, when the sun was strong. The first distillation of a lunar herb — plants like white poppy or cleavers, assigned to the Moon — might be timed to a Monday, in a lunar hour, with attention to the Moon’s phase. Calcination of the plant’s salt, a Saturnine operation associated with reduction and purification, was sometimes assigned to Saturday or to a Saturn hour. The Opus Magnum tradition and later texts like the 1659 English translation of Oswald Croll’s Basilica Chymica make these timings explicit. This was not superstition layered onto chemistry. For these practitioners, the timing was chemistry — a chemistry that included the whole cosmos as a reactive environment.

The Picatrix and the Harder Question

If you want the full depth of the system — and the full strangeness — you go to the Picatrix. Originally an Arabic text, the Ghayat al-Hakim (roughly tenth or eleventh century), translated into Latin in the thirteenth century at the court of Alfonso X of Castile, the Picatrix is a grimoire of astrological magic that treats planetary hours with an intensity that makes Paracelsus look casual. Here the hours are not scheduling tools. They are windows. The correct planetary hour is the moment when a specific cosmic current is most accessible, and the text provides detailed instructions for images, suffumigations, and preparations to be performed inside those windows. The herbalism that emerges from this tradition is not about the plant alone. It is about the plant-at-a-moment, the plant understood as a temporal as well as botanical entity.

Which brings us to the honest question you are probably already asking.

Whether You Should Actually Do This

Here is what I think, stated plainly. The metaphysics are not proven and I will not pretend otherwise. There is no controlled study showing that Saint John’s Wort harvested on a Sunday during a solar hour contains measurably different hypericin concentrations than the same plant harvested on a Tuesday. If that kind of evidence is what you need before you engage with a practice, this system is not for you, and that is a legitimate position.

But something else is true simultaneously. The planetary hours system does something to the practitioner that is not nothing. It forces a quality of attention that casual harvesting never demands. When you have decided that you will harvest your lemon balm — a Mercury plant in the classical schema — during a Mercury hour on a Wednesday, when Mercury is well-placed, you have committed yourself to watching. You are watching the sky, watching the season, watching the specific character of the morning. You are not wandering out to the garden when you happen to remember. You have made the work intentional in a structural way. That intentionality changes what you notice. It changes what you remember. And in a craft tradition where observation is everything — where the difference between a mediocre tincture and an extraordinary one often comes down to whether the practitioner was actually present — that is not a trivial effect.

This is, interestingly, not far from what the more serious contemporary practitioners of spagyrics argue. Robert Bartlett, whose Real Alchemy remains one of the clearest modern introductions to the spagyric work, is careful and empirical in tone, but he does not dismiss the timing traditions. He holds them the way a good craftsperson holds a rule of thumb: with respect, with flexibility, and with attention to whether the work confirms or complicates the principle.

How to Begin, Practically

If you want to work with this system, start with the day rulerships before you touch the hours. Learn which plants correspond to which planets. The standard English reference for this is Nicholas Culpeper’s Complete Herbal (1653), which assigns a planetary ruler to virtually every plant in the British tradition. Culpeper’s assignments are sometimes disputed and occasionally idiosyncratic, but they are internally consistent and historically rooted. Use them as a starting point, not a final word.

Then pick one plant and one operation. Say you are making a spagyric tincture of rosemary, a solar herb in Culpeper’s system. Plan to begin the maceration on a Sunday. Note what solar hour that falls in, even if you do not yet trust the hour system fully. Write it down. Make the tincture with full attention to the day, the light, the season. When you eventually calcine the salt — and if you are making a true spagyric preparation, you will calcine the salt — consider doing that on a Saturday, in a Saturn hour, acknowledging the Saturnine character of reduction and return to ash.

A word of caution that must be said plainly: rosemary is generally considered safe for external use and in culinary quantities, but like all spagyric and herbal preparations, concentrated tinctures are a different matter. Do not ingest anything you have made without consulting a qualified medical professional. The tradition demands rigor, and rigor includes knowing the limits of self-instruction.

What you are building, over months and years of this practice, is something the old texts call experience — not the soft modern word that means having done something once, but the hard alchemical word that means a body of observed, recorded, repeated encounter with matter across time. The planetary hours give that time a shape. They give your attention a structure to move inside. Whether the cosmos responds to that structure literally or whether the response is entirely internal to the practitioner — that question may be unanswerable. Work the system long enough and you may stop caring which it is. The work either becomes real or it doesn’t. Stand outside before dawn. Know what hour you are in. Begin.

Frequently Asked Questions

What is the Chaldean order in planetary hours?

The Chaldean order is the fixed sequence of planets used to assign hours within each day: Saturn, Jupiter, Mars, Sol, Venus, Mercury, Luna, repeating. The planet ruling the first hour of any day is the same planet that rules that day itself. This sequence determines which planet governs each of the twenty-four hours.

Did Paracelsus use planetary timing for herbalism?

In the early sixteenth century, Paracelsus built his medical cosmology on correspondences between planets, metals, organs, and plant families. He held that the same principle animating a planet animated plants under its rulership. Timing harvests and operations to planetary days and hours was, for him, not incidental but central to making the work coherent.

What does the Picatrix say about planetary hours?

The Picatrix, originally an Arabic text from the tenth or eleventh century and translated to Latin in the thirteenth century at the court of Alfonso X of Castile, treats planetary hours as windows when specific cosmic currents are most accessible. It provides detailed instructions for images, suffumigations, and preparations to be performed during these hours.

Where should I start if learning planetary timing for spagyrics?

Begin with day rulerships and planetary correspondences before studying the hourly system. Nicholas Culpeper’s Complete Herbal (1653) is the standard English reference, assigning planetary rulers to plants in the British tradition. Pick one plant and one operation—such as beginning a solar herb’s maceration on Sunday—and work with full attention to season and light.