This is from Kevatta Sutta :
Consciousness without feature,
without end, luminous all around:
Here water, earth, fire, & wind
have no footing.
Here long & short
coarse & fine
fair & foul
name & form are all brought to an end.
With the cessation of [the activity of] consciousness
each is here brought to an end.'"
Note  Points to MN 49 and in a note in MN49 vinnanam anidassanam was explained.
This is note 9 from MN 49
Consciousness without surface (viññanam anidassanam): This term appears to be related to the following image from SN 12.64:
"Just as if there were a roofed house or a roofed hall having windows on the north, the south, or the east. When the sun rises, and a ray has entered by way of the window, where does it land?"
"On the western wall, lord."
"And if there is no western wall, where does it land?"
"On the ground, lord."
"And if there is no ground, where does it land?"
"On the water, lord."
"And if there is no water, where does it land?"
"It does not land, lord."
"In the same way, where there is no passion for the nutriment of physical food ... contact ... intellectual intention ... consciousness, where there is no delight, no craving, then consciousness does not land there or grow. Where consciousness does not land or grow, name-&-form does not alight. Where name-&-form does not alight, there is no growth of fabrications. Where there is no growth of fabrications, there is no production of renewed becoming in the future. Where there is no production of renewed becoming in the future, there is no future birth, aging, & death. That, I tell you, has no sorrow, affliction, or despair."
if you can learn some of the Sanskrit it really can help
Some research if only reading is your tool for dharma can be done via pre 10th India.