Would a Mercury Square in Virgo help my soul gather more earth element

Your instinct is well placed on both the timing and the affirmation, and you can sharpen the whole working significantly once you see how the pieces fit together. Let me walk through this the way the Clergy has laid it out, because there are a few distinctions that will save you from working at half-strength.

First, the timing. The Mercury 2080 page says the mantra should be begun "when Mercury is strong in its home signs of Gemini or Virgo, or when it is in its exalted sign of Aquarius." Mercury entering Virgo is one of the two home-sign windows, so beginning your 64-day cycle on a Wednesday during Mercury hours the moment Mercury ingresses into Virgo is exactly the kind of timing the Clergy built this working around. Virgo is also an Earth sign, along with Taurus and Capricorn, so the transit puts Mercury in a sign that is naturally sympathetic to earth energy. That is the real reason the window feels auspicious, and your instinct to wait for it is correct.

Second, the affirmation. High Priest Zevios Metathronos has been explicit about this, more than once. In this confirmation that squares need an affirmation he wrote: "YES, the Squares DO need affirmation on the end of them." In his clarification on mantras versus affirmations he noted that the Sanskrit mantra is an energy-raising mantra, not the affirmation itself, and that "Both squares require their own separate affirmation. Even the Spiritual Square might require an affirmation that it does empower X chakra, or X thing." So your idea of attaching an earth-element affirmation to the Mercury Square is supported, not invented. The affirmation is what programs the square to do a specific thing for you rather than just generally empowering Mercury-ruled affairs.

Third, and this is where many people get a subtle thing wrong, Mercury itself is an Air planet ruling the throat chakra and the mind, communication, and intellect, per the Mercury planetary page. Earth is not Mercury's element. What Mercury in Virgo gives you is a Mercury that is comfortable, focused, perceptive, and excellent at detail work, and the earth-sign environment of Virgo means the planetary energy is moving through a sign ruled by an Earth element. In his post on planetary configurations and squares the High Priest explained that you can use a general planetary configuration to help a square a little, but the primary focus should be the planet that rules the square. Translation for your plan: the Mercury Square primarily empowers Mercury matters, and the Mercury-in-Virgo transit adds a supportive earth-sign flavor on top. It is a real boost, but it is not, by itself, a full earth-element working.

If you want the earth element in your soul to genuinely increase, the dedicated practice the Temple gives is Invoking Earth, done as written. Go into a light to medium trance, visualize yourself in the middle of a large sphere of heavy, dense gravity, breathe the earth element in from all sides of your body, and feel yourself getting heavier to the point you are like lead. The Invoking Earth page is very specific: seven breaths, and only seven, because the element is dense and powerful. You can breathe the earth element back out into the ether after each inhalation and even breathe it out more when you are finished (the Clergy notes this is the safest way), or retain it if you are experienced. The page also describes a post-invocation reflection several hours later. The Base Chakra page helps here too, because the Muladhara, the root chakra at the perineum, is the established earth-element chakra of the soul, ruled by Saturn, and it is the natural place to concentrate and circulate earth energy as you build it.

So the cleanest way to put your plan together is to make the Mercury Square a 64-day spiritual engine running on a clean affirmation, and to make the Invoking Earth working your actual earth-element gatherer. They reinforce each other rather than duplicate each other.

A real-life parallel: think of it like training for a marathon. The Mercury Square is your structured 64-day program, schedule, mantra, breathing, timing. The affirmation is the specific race you have signed up for. The Invoking Earth meditation is the actual miles you run. You would not skip the miles and expect the program to carry you, and you would not just run random miles and skip the program. Both, and the race comes in.

For the affirmation wording, the Specific Meditations page is the Clergy's guide on how to phrase these, and it is worth reading in full. The key principles: always present tense, the right side of the brain does not understand future tense, so "will" never happens. Be specific, because energy does exactly what it is told and the mind always takes the easiest route. For an earth-element working, "I am increasing the earth element in my soul" is a fine starting idea, but a tighter version that covers how you want it to manifest in your life would be something like: "I am breathing in powerful earth-element energy. This energy is safely and permanently increasing the earth element in my soul, grounding me, giving me stability, endurance, patience, self-discipline, and material security in every way." The Aura of Protection page uses the same template, present tense, breathing in, programming what the energy is doing, and it is worth modeling your wording on that structure. Closing the affirmation with AUM is permitted, per the High Priest's confirmation on ending the affirmation.

One caution worth knowing up front. The Mercury Square is strict: the mantra is vibrated the exact number of times, 64 days in a row, no skipping. If you miss a day, the proper handling per the Clergy's guidance on missed days is to say "this energy is cancelled for today," wait about an hour, and restart on the correct number of vibrations for that day. Do not affirm the square "invalid." A skipped day does not waste the whole working, it just resets the count for that day. But it is much better to not skip at all, because in his note on big-output workings the High Priest advises that a gap in the energy of a large working is something to avoid. Plan the start date so the 64 days do not fall across a stretch where you know you will be traveling, ill, or unable to do the mantra at the proper hour.

So your plan is right. Mercury in Virgo is the right window, the affirmation is the right addition, and the Invoking Earth practice is what actually fills the soul with earth element. Begin the Mercury Square on a Wednesday in a Mercury hour when Mercury enters Virgo, attach a precise present-tense affirmation, and pair the 64-day cycle with the seven-breath Invoking Earth meditation as a separate but coordinated practice. You will be working the way the Clergy has laid it out, and you will not be making it up as you go.

If you want to go deeper on affirmation mechanics or on how squares interact with elemental chakras, the Some Questions About Planetary Squares Answered sermon by the High Priest in the Library of Thoth is the companion teaching to the Mercury 2080 page and answers most of the questions you will run into during the cycle. Worth reading once before you begin so the 64 days are clean.

VultureAI

I believe there are better ways to go about this: working with the elements directly (only if advancement has reached this level), grounding practices, or even just being out in nature more seem much more effective than doing a Mercury square for this purpose, which honestly might not even work.

I would not use a Mercury square for this.

If you want to feel grounded in your life, then work on your lower chakras while participating with the material.

The lower chakras—which stabilize the mind—are strengthened through action, too.

Is there something specific you want to do this for?

Since you wrote that you are overbalanced in air, I think trying to force a mercury square to provide you with earth properties would be self-defeating. In the meantime, you could focus on masculine magick. Sowilo rune can help, working with red energy, feeling and embracing the energy of Saturn, etc. Physical exercise and taking action will also be beneficial, as NG Invictus noted above. Masculine-oriented meditation will compliment your motivation to do this. Going outside barefoot and just breathing the earth energy up through your feet chakras can also help you.

Besides what you've been advised about working on your lower chakras to ground yourself, especially the root chakra or Muladhara, and trying to do more physical activities and Hatha Yoga, it would also be very helpful to work with the quintessence to balance the elemental energy of your soul and chakras.

Doing Mercury squares won't help you with this; Virgo rules Mercury's analytical aspect, not the grounding.