本来無一物 says there is nothing for you to cling to, because all things have been empty all along. 本来 is how things have always stood, not where they came from. 無一物 is not a single thing, and the dictionaries end on a mind that nothing holds. Zen teachers warn that saying the words is not the point. Whether you take it as a teaching or as a reminder to let go is yours.
The line is the third of the verse that, in Chan legend, won the illiterate Huineng 惠能 the Sixth Patriarch's robe; it is absent from the oldest surviving text of the Platform Sutra, a Dunhuang manuscript copied in the ninth century, is quoted in a record of the 850s, stands in the verse in a Chan history of 952, and has been in the sutra's received text since 1291.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 本来無一物.