I hope it's alright that I talk about the Roman empire from c.500-700, a period supposedly after the 'fall' of 'Rome' in 476, yet in reality it was a time when the Roman empire continued to flourish and remained the predominant Christian power in the Mediterranean world. Some people would prefer to call it the 'Byzantine' empire, but hopefully you will indulge me here. As you will see, it is also very difficult to tease out what the Romans actually knew, so this answer might in fact make things more confusing, apologies in advance!

So what did the Romans know? The first source to look at is the Christian Topography of Cosmas Indicopleustes, a native of Alexandria from the early sixth century. He was a well-travelled man, being familiar with both Persia and Ethiopia and in this strange geographical/theological treatise he described a country called Tzinitza, which seems to be China:

Yet if Paradise did exist in this earth of ours, many a man among those who are keen to know and enquire into all kinds of subjects, would think he could not be too quick in getting there: for if there be some who to procure silk for the miserable gains of commerce, hesitate not to travel to the uttermost ends of the earth, how should they hesitate to go where they would gain a sight of Paradise itself? Now this country of silk is situated in the remotest of all the Indies, and lies to the left of those who enter the Indian sea, far beyond the Persian Gulf, and the island called by the Indians Selediba and by the Greeks Taprobana. It is called Tzinitza, and is surrounded on the left by the ocean, just as Barbaria is surrounded by it on the right.

The Indian philosophers, called the Brachmans, say that if you stretch a cord from Tzinitza to pass through Persia, onward to the Roman dominions, the middle of the earth would be quite correctly traced, and they are perhaps right. For the country in question deflects considerably to the left, so that the loads of silk passing by land through one nation after another, reach Persia in a comparatively short time; whilst the route by sea to Persia is vastly greater. For just as great a distance as the Persian Gulf runs up into Persia, so great a distance and even a greater has one to run, who, being bound for Tzinitza, sails eastward from Taprobana; while besides, the distances from the mouth of the Persian Gulf to Taprobana; and the parts beyond through the whole width of the Indian sea are very considerable. He then who comes by land from Tzinitza to Persia shortens very considerably the length of the journey. This is why there is always to be found a great quantity of silk in Persia. Beyond Tzinitza there is neither navigation nor any land to inhabit.

I haven’t looked at this text too much, but I’ve read that ‘for his own theological reasons, he refused to use the maps derived from Ptolemy and instead took up again the very ancient geography of Ephorus (from around 350 b.c.e.)’^1 You will have to ask a classicist to explain whether Cosmas’ knowledge was entirely derived from older literary sources, but I think that it’s more likely that Cosmas’ understanding was the result of his contemporary knowledge, since as far as I know Tzinitza was not attested to before him. Elsewhere he noted that many of his stories were told to him by traders, so I don’t see any reason to argue otherwise here. His description however is not very detailed, which suggests that he was operating with his own theological thinking at the forefront of his mind and because of the unclear information his sources provided about what China was like. To serve as a comparison, we can also take a brief look at Ammianus Marcellinus’ earlier account from 391:

The Seres themselves live quietly, always avoiding arms and battles; and as ease is pleasant to moderate and quiet men, they give trouble to none of their neighbours. Their climate is agreeable and healthy; the sky serene, the breezes gentle and delicious. They have numbers of shining groves, the trees of which through continued watering produce a crop like the fleece of a sheep, which the natives make into a delicate wool, and spin into a kind of fine cloth, formerly confined to the use of the nobles, but now procurable by the lowest of the people without distinction.

Like Cosmas’ story, this was tinged with Ammianus’ own thinking and biases – this historian wanted everything to go back to the good old days, when Romans were less decadent, hence his moralising here about silk being cheap and thus even available to commoners! As such, I think it is difficult to tease out what he (or anyone else) actually thought. Ammianus certainly knew about China, but his words can hardly be said to be a full description nor can we be sure that he told us everything he knew. This is a broader problem with all the sources I discuss here, since just because someone wrote down a description of China, it doesn’t mean that it was representative of their views!

The next source is very famous, the Gothic War of Procopius, specifically book 8 that was written c.554 or later:^2

At this time some monks arrived from India, and when they learned that the emperor Justinian was eager to find a way so that the Romans no longer had to buy silk from the Persians, they came before the emperor and declared that they could arrange it so that the Romans would no longer have to purchase this item from their enemy the Persians, or indeed from any other people. For they had spent much time in a land situated far to the north of the nations of India which is called Serinde, and there they had learned exactly by what process silk could be produced in Roman lands too. The emperor questioned them in detail and sought to discover whether this was true. The monks then explained that the makers of silk were certain worms that knew how to do this by their nature, which compelled them to produce it continually.

While it would be impossible to bring these worms here alive, it could be done easily with their offspring, which consisted of countless eggs. Men cover these eggs with dung long after they are laid and, by heating them so for a sufficient time, they hatch the animal itself. When they said this, the emperor promised to give the men great gifts and persuaded them to prove their words through action. So they went back to Serinde and brought the eggs to Byzantion, where they transformed them into worms in the manner just described, feeding them on mulberry leaves. From that time onward silk has been produced in the lands of the Romans.

This often taken as evidence that the Romans had no means to produce silk before this point, but this point is a dubious one. Once again I am way beyond my comfort zone, so let me just quote Julia Galliker’s PhD thesis (2015) here:

While silk cultivation most likely developed gradually in the empire, we have no specific documentary evidence of sericulture until the eleventh century. Some historians have suggested earlier cultivation of silk fibre at various locations including Syria and the Peloponnese. The argument for Syrian silk cultivation is based on Prokopios’ report that silk garments had long been made in Berytos and Tyre. Muthesius suggested that Syria supplied raw silk to Byzantium based on a tentative place name identification in a Chinese text dated before 429. Evidence for the transfer of moriculture and sericulture from Syria to al-Andalus after 726 is also indirect and is based on a thirteenth-century reference to Syrian mulberry trees.

Back to the main point, Procopius knew where silk came from, but it is debatable whether he was using contemporary knowledge or just what had long been known within the empire. If this is an accurate enough reflection of what actually happened, we can perhaps speculate that the imperial government was aware of the economic forces driving the production of silk and was contemplating creating an imperial monopoly, but we certainly can’t say anything beyond that.

End of part one

As /u/Shlin28 so wonderfully covered the Roman Side, I'll cover the Chinese Side.

Edward H. Schafer's Iranian Merchants in Tang Tales though briefly, mentions the cosmopolitian nature of Tang Dynasty China. That is to say that there were quarters within Chang'An (the capital of the Tang) where foreign merchants from Iran and the Taklamakan Desert (Tarim Basin) would stay while in China.

Now, the problem is that most of these accounts are from after 476 and well into the 600s and 700s and many of the Chinese never directly dealt with the Byzantines as most of the Merchants were Iranian.

To make matters even more complicated, most of the Taklamakan Desert at the time was occupied by Turkic Uighers, the Sogdians, and a few other Oasis societies, all of which were found to have among other types of coinage, Roman coins. Meaning that at the very least trade was conducted between the Tang and the Byzantines. Albeit through intermediaries like the Iranians who used intermediaries like the Sogdians to communicate between the Tang and the Uighurs (later Turks) within the Tarim Basin.

The problem is that it's actually rather difficult to find any impression on Chinese on the Romans. Because there seemingly is very little the Tang had written about the Romans, I posit that the system of trade between China and Rome operated not directly but rather through multiple cities and cultures through the Silk Road instead of direct contact may be partially responsible for this. What we do know is that there was indeed evidence of trade between the two groups of people through archaeological evidence that's littered throughout the Taklamakan Desert (a wonderful place to preserve your things btw). What we don't know is if there were Romans who ended up in China or vice versa. Due to the sheer distance and the multiple groups of people through what people consider the Silk Road, it's rather difficult to gauge whether or not there were.

Maybe one day there will be more academic work done on this, but the field of Silk Road and Tarim Basin cultures is relatively unstudied.

Sources:

1. Edward H. Schafer, Iranian Merchants in Tang Tales

2. Valerie Hansen, The Silk Road: A New History