Sounds like a clever idea, but don’t let the calculator eat the soul of the piece. First, pick a spot that feels like a natural extension of the furniture’s line—maybe the back of a chair’s seat cushion or the underside of a table top. Gently carve a shallow recess with a hand‑saw and a fine chisel; a router would strip the patina. Use a bit of soft‑wood filler to smooth the cavity, then sand with a fine grit that matches the existing finish. Once the calculator sits snugly, fill the gap with a contrasting wood—something that tells a story of its own, like a reclaimed cherry—so the old meets the new without a modern swoop. Finally, secure the piece with a discreet set screw or a small brass bracket, hidden beneath the surface. It’s all about respecting the layers, not bulldozing them. And if the calculator’s gears start to squeak, a little beeswax on the shafts keeps the old mechanics humming.