[One] must get accustomed to discovering the traces (vestigia) of spiritual things in bodies in such a way that when he turns upward from here and starts climbing (ascendere coeperit) with reason as his guide in order to reach the unchanging truth itself through with these things were made. De Trinitate, XII:5, translation of Edmund Hill, OP.
Then moving ahead to Francis:
In whatever way it seems good to you to please the Lord God and to follow his footprint (sequi vestigiam) and his poverty, do it with my blessing of the Lord God and my obedience. Letter to Brother Leo, my translation.
And then to Bonaventure:
For it is in harmony with our created condition that the universe itself might serve as a ladder by which we can ascend (scala ad ascendum) into God. Among created things, some are vestiges (vestigium), some images, some are bodily, others are spiritual...let us place the first step of our ascent at the bottom, putting the whole world of sense-objects before us as a mirror through which we may passs to God, the highest creative Artist. Itinerarium Mentis in Deum,, I: 2, 9, translation of Zachary Hayes, OFM.