I think the quote in Wikipedia is Sheng-yen's paraphrase of The Fourth Patriarch Tao-hsin who quoted from the Manjushri sutra:
The Fourth Patriarch Tao-hsin 道信（580-651 ）
wrote Ju-tao anhsin yao fang-pien men 入道安心要方便
門. The Methods for Entering the Path and Calming
the Mind. In it, he quoted from the Lankavatara Sutra
and the Wen-shu shuo po-jo ching 文殊說般若經. The
Prajna Sutra Spoken by Manjusri. He stresses the
importance of tso-ch'an for the beginner, with
emphasis on the right posture. The neophyte must then
contemplate the five skandhas the material skandha of
form (the elements), and the four mental skandhas :
feeling, perception, phenomena, and consciousness.
The Manjusri Sutra says, "He should contemplate the
five skandhas as originally empty and quiescent,
non-arising, non-perishing, equal, without
differentiation. Constantly thus practicing, day or
night, whether sitting, walking, standing or lying
down, finally one reaches an inconceivable state
without any obstruction or form. This is the Samadhi
of One Act (I-hsing sanmei) 一行三昧."
TSO-CH'AN
By Master Sheng-Yen
Strangely though, I looked for a translation of the Manjusri Sutra to see for myself what it says originally, and what I read there about the Samadhi of One Act doesn't talk about skandhas, it seems to be very different:
Mañjuśrī asked, “World-Honored One, what is called the One Action Samādhi?”
The Buddha replied, “The dharma realm has the one appearance. Focusing one’s mind on the dharma realm is called the One Action Samādhi. If, among good men and good women, there are those who aspire to enter the One Action Samādhi, they should first hear prajñā-pāramitā and next train and learn it accordingly. Then they will be able to enter the One Action Samādhi, which fits the conditions of the dharma realm: indestructible, inconceivable, with no regress, no hindrance, and no appearance. If good men and good women aspire to enter the One Action Samādhi, they should sit properly in an open place, facing the direction of a Buddha, abandon distracting thoughts and appearances, focus their minds on that Buddha, and keep saying His name. If they can continue, thought after thought, thinking of one Buddha, they will be able to see, in their thinking, past, future, and present Buddhas. Why? Because the merit acquired from thinking of one Buddha is immeasurable and boundless, no different from the merit acquired from thinking of innumerable Buddhas or thinking of the inconceivable Buddha Dharma.
The Mahaprajnaparamita Sutra taught by Manjushri
A little earlier though in ibid. is the passage which might be paraphrased as being about skandhas:
Mañjuśrī said,
“If I could say that I abide in prajñā-pāramitā, this would be a
perception founded on the view that one has a self. Abiding in a
perception founded on the view that one has a self means that
prajñā-pāramitā has a place. That I do not abide in prajñā-pāramitā is
also [a perception] founded on the view that one has a self, and is a
place as well. Free from these two places [subject and object], I
abide in not abiding, like Buddhas abiding in the inconceivable state
of peace and silence. Such an inconceivable state is called the
dwelling of prajñā-pāramitā. In the dwelling of prajñā-pāramitā, all
dharmas have neither appearance nor act.
“Prajñā-pāramitā is inconceivable. The inconceivable state is the dharma realm, which has no appearance. Having no appearance is the inconceivable state; the inconceivable state is prajñā-pāramitā. Prajñā-pāramitā and the dharma realm are the same, not distinct. Having neither differentiation nor appearance is the dharma realm; the dharma realm is the realm of prajñā-pāramitā. The realm of prajñā-pāramitā is the inconceivable state; the inconceivable state is the realm of no birth and no death.”
Mañjuśrī continued,
“The realm of a Tathāgata and the realm of a self are the appearance of non-duality. Those who practice prajñā-pāramitā in this way do not seek bodhi. Why not? Because bodhi, which is free from appearances, is prajñā-pāramitā.
“World-Honored One, to know the appearances of a self means not to be captivated by it. Not knowing and not being captivated by anything is what Buddhas know. The inconceivable [state of] not knowing and not being captivated by anything is what Buddhas know. Why? They know that the true nature of everything has no appearance. Then what drives the dharma realm? What in its true nature has neither self-essence nor attachment is called no thing[2] and is free from place, dependency, and fixity. Freedom from place, dependency, and fixity means having neither birth nor death. Having neither birth nor death is the virtue of any saṁskṛta or asaṁskṛta dharma. With this knowledge, one will not elicit perception. Without perception, how can one know the virtue of any saṁskṛta or asaṁskṛta dharma? Not knowing[3] is the inconceivable state. The inconceivable state is what Buddhas know, such as neither grasping nor not grasping, seeing neither the appearance of past, present, or future, nor the appearance of coming or going, and grasping neither birth nor death, neither cessation nor perpetuity, neither arising nor acting. This knowledge is called the true wisdom-knowledge, the inconceivable wisdom-knowledge. Like the open sky, with neither appearances nor features, in unequaled equality, it makes no comparison, neither this against that nor good against evil.”
The Buddha told Mañjuśrī,
“This knowledge is called the wisdom-knowledge that never fades.”
Now for your question -- "What is meant by empty, non-arising, etc.?"
I'm not sure I can explain it in my own words.
The four noble truths suggest that suffering (and desire) arise and cease -- and the goal is cessation, or non-arising.
In a similar way I think the quote you're asking about is saying to contemplate the skandhas as "non-arisen".
A complication (which may or may not be relevant) might be that according to some "perfect wisdom" doctrine, it isn't correct to talk about things (dhammas including skandhas) as arising and ceasing -- because, they have no own-existence, they're like dreams.
